Geology of India [Second ed.]

Table of contents :
Contents
1. Physical features,
2. Stratigraphy of India,
3. The Archaean System,
4. The Dharwar System,
5. The Cuddapah System,
6. The Vindhyan System,
7. The Cambrian System,
8. The Silurian, Devonian and Lower Carboniferous Systems,
9, 10. The Gondwana System,
11. The Upper Carboniferous and Permian Systems,
12. The Triassic System,
13. The Jurassic System,
14, 15. The Cretaceous System,
16. The Deccan Trap,
17. The Tertiary Systems,
18. The Eocene System,
19. The Oligocene and Lower Miocene Systems,
20. The Siwalik System - Middle Miocene and Lower Pliocene,
21-24. The Pleistocene System,
25. Physiography,
26. Economic Geology,
27. Geology and Stratigraphy of Kashmir.

Citation preview

GEOLOGY OF IN D IA

BY

D. N . W A D IA , M.A., B.Sc., F.G.S., F.R.G.S., F.R.A.S.B. G E O L O G IC A L S U R V E Y O F I N D J / .

W IT H IL L U ST R A T IO N S

M ACM ILLAN AND CO., L IM IT E D ST. M A R T IN ’S ST R E E T , LONDON 19 44

C O PY R IG H T

To A.

First Edition 1919 Revised 1926. Second Edition 1939. Reprinted 1944.

P R IN T E D

AND

P U B L IS H E D IN

GSEAT

AND

F.

IN HEAVEN, THESE PAGES ARE INSCRIBED

B R IT A IN

PREFACE As a lecturer in Geology to students preparing for the Punjab Uni­ versity Examinations I have constantly experienced great difficulty in the teaching of the Geology of India, because of the absence of any adequate modern book on the subject. The only work that exists is the one published by the Geological Survey of India in 1887, by H. B. Medlicott and W. T. Blanford, revised and largely rewritten by R. D. Oldham in 1893—a quarter of a century ago. Although an excellent official record of the progress of the Survey up to that time, this publi­ cation has naturally become largely out of date (now also out of print) and is, besides, in its voluminous size and method of treatment, not altogether suitable as a manual for students preparing for the Uni­ versity Examinations. Students, as well as all other inquirers, have, therefore, been forced to search for and collect information, piece­ meal, from the multitudinous Records and Memoirs of the Geological Survey of India. These, however, are too numerous for the diligence of the average student—often, also, they are inaccessible to him—and thus much valuable scientific information contained in these admir­ able publications was, for the most part, unassimilated by the student class and remained locked up in the shelves of a few Libraries in the country. I t would not be too much to say that this lack of a handy volume is in the main responsible for the almost total neglect of the Geology of India as a subject of study in the colleges of India and as one of independent scientific inquiry. The object of the present volume is to remedy this deficiency by providing a manual in the form of a modern text-book, which sum­ marises all the main facts of the subject within a moderate compass. I t is principally a compilation, for the use of the students of Indian Geology, of all that has been published on the subject, especially in­ corporating the later researches and conclusions of the Geological Survey of India since Oldham’s excellent edition of 1893. In a subject of such proportions as the Geology of India, and one round which such voluminous literature exists, and is yearly growing, it is not possible, in a compendium of this nature, to aim at perfection of detail. Nor is it easy, again, to do justice to the devoted labours of

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the small body of original workers who, since the ’50’s of the last century, have made Indian Geology what it is to-day. By giving, however, in bold outlines, the main results achieved up to date and by strictly adhering to a text-book method of treatment, I have striven to fulfil the somewhat restricted object at which I have aimed. In the publication of this book I have received valuable help from various quarters. My most sincere thanks are due to Sir T. H. Holland, F.R.S., D.Sc., for his warm sympathy and encouragement. To Dr. E. H. Pascoe, D.Sc.^ Director of the Geological Survey of India, I offer my grateful acknowledgments for the loan of blocks and plates from negatives for the illustrations in the book, and for per­ mission to publish this volume. My indebtedness to Mr. C. S. Middlemiss, C.I.E., F.R.S., retired Superintendent of the Geological Survey of India, the doyen of Indian Geologists, I can never suf­ ficiently acknowledge. His guidance and advice in all matters con­ nected with illustrations, correction of manuscript and text, checking of proofs, etc., have been of inestimable value. Indeed, but for his help several imperfections and inaccuracies would have crept into the book. I have also to offer my warm thanks to Dr. G. E. Pilgrim, D.Sc., for his helpful criticisms and valuable suggestions in revising the Tertiary Systems. In the end, I tender my grateful acknowledgments to Messrs. Macmillan for their uniform courtesy. D. N. WADIA. J am m u,

December, 1916,

POSTSCRIPT T h e writing of the first edition of this book was completed in 1916, since when there has bt;en no opportunity of revising it on an ade­ quate scale, or or incorporating in it the results of the activities of the Geological Survey of India in tiie last twenty years as well as of the steadily increasing volume of extra-departmental work published in various branches of the Geology of India. The present edition, though not considerably enlarged in bulk, is thoroughly revised and brought up to date by incorporating new research. A geological map of India, on the scale of 96 miles = 1 inch, is added, embodying all the recently surveyed regions in the Hima­ layas, Rajputana, Assam and other parts of India. I t is my pleasant duty to tender my grateful acknowledgments for valuable help received from various quarters—to Dr. A. M. Heron, D.Sc., F.R.S.E., Director, Geological Survey of India, for permission to publish the revised book and for his helpful criticisms and sug­ gestions ; to Professor B. Sahni, Sc.D., F.R.S., for the revision of the Chapters dealing with the Gondwana System and for a critical ex­ amination of the lists of fossil floras of India ; and to Mr. Percy Evans for many important suggestions regarding several sections of the book and for assistance in the revision and correction of proofs. To many of my colleagues of the Geological Survey of India I am indebted for much ungrudging assistance and for their helpful attitude throughout in the production of this edition.

D. N. WADIA. C alcutta,

12f/t July, 1937.

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CONTENTS CHAPTER I P h y s ic a l F e a t u r e s

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Geological divisions of India ; their characters and peculiarities ; types of the earth’s crust exemplified by these divisions. Physical characters of the plains of India. Rajputana a debatable area. Mountains of India ; the Himalayan mountains ; physical features of the Himalayas ; meteor­ ological influence of the Himalayas. Limits of the Himalayas. The Byntaxial bends at the N.W. and S.E. Classification of the Himalayan ranges, (1) Geographical, (2) Geological. Other ranges of extra-Peninsular India. Mountain ranges of the Peninsula ; Vind'.iyan mountains ; the Satpura range ; the Western Ghats ; the Eastern Ghats. Glaciers : glaciers of the Himalayas ; their size ; limit of Himalayan glaciers ; peculiarities of Himalayan glaciers ; records of past glaciation in the Himalayas. The drainage system : the easterly drainage of the Peninsula ; the Himalayan systeni o f drainage not a consequent drainage ; the Himalayan watershed ; the transverse gorges of~the Himalayas ; river-capture or “ piracy ” ; the hanging valleys of Sikkim. Lakes ; the lakes of Tibet, Kashmir and Kumaon ; salinity of the Tibetan lakes ; their desiccation ; the Sambhar lake ; the Lonar lake. The Coasts of India ; submerged mountain-chain and valleys of the Arabian Sea. Volcanoes: Barren Island ; Narcondam ; P o p a; Koh-i-Sultan. Mud-volcanoes. Earthquakes: the earthquake zone of India ; the Assam earthquake ; the Kangra earthquake ; Bihar earthquake ; Quetta earthquake. Local alterations of level; recent elevation of the Peninsular tableland ; other local alterations; sub­ merged forest of Bombay; alterations of level in Cutcli; the Himalayas yet in a state of tension. Isostasy. Denudation ; the monsoonic alter­ nations ; the lateritic regolith; general character of denudation in India sub-tropical, desert-erosion in Rajputana. Peculiarity of river-erosion in India : the river-floods. Late changes in the drainage of Northern In d ia; the Siwalik river, its dismemberment into the Indus and Ganges; reversal of the north-westerly flow of the Ganges. References. CHAPTER II S t r a t ig r a p h y o f I n d ia — I n t r o d u c t o r y

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Difficulty of correlation of the Indian formations to those of the world ; principles involved. The different “ facies ” of the Indian formations. Provincial faunas. Radio-active minerals as an aid to stratigraphy. The chief geological provinces of India : the Salt-Range ; tho N.W. Himalayas ; the Central Himalayas ; Sind ; Rajputana ; Burma and Baluchistan ; the Coastal tracts. Method of study of the geology of India. Table of the geological formations of India. References. CHAPTER III T he A rchaean System

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General. Distribution of the Archaean of India ; petrology of the Arch­ aean system ; the chief petrological types : gneisses ; granites ; syenites ;

CONTENTS

CONTENTS

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Charnockite, Khondalite, Gondite, Kodurite, calc-gneisses and calciphyres, etc. Classification of the Archaean system. Bengal gneiss ; types of Ben­ gal gneiss. Bundelkhand gneiss. The Charnockite series ; petrological characters of the Charnockite series ; their microscopic characters. Arch­ aean of the Himalayas. References.

Chitral. (iv) Burma—the Northern Shan States ; Ordovician ; Silurian —Namshim series, Zebingyi series ; Silurian fauna of Burma ; Devonian; the Devonian fauna ; the Wetwin slates. Carboniferous of Burma ; the Plateau limestone ; Fusulina limestone. Table of the Palaeozoic forma­ tions of Burma. Physical changes at the end of the Dravidian era. Re­ ferences.

CHAPTER IV T h e D h arw a r S y stem -

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CHAPTER IX -

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General. Outcrops of the Dharwar rocks ; the lithology of the Dharwars ; plutonic intrusions in the Dharwars ; crystalline limestones originating by the metasomatism of the gneisses. Distribution of the Dharwar system. Type-area Dharwar ; Rajputana : the Aravalli mountains ; the Aravalli scries ; the Raialo series; the Shillong series ; the Dharwar rocks of the Central Provinces; the manganiferous deposits of the Dharwar system—the Gondite and the Kodurite series : Bihar and Orissa—the Iron-ore series. Manganese ores of the Dharwar system. The Dharwar system of the Himalayas. The Vaikrita series; Salkhala series; Jutogh series and Daling series. Homotaxis of the Dharwar system. The Archaean-Dharwar controversy. Economics. References.

T h e Cu d d a p a h S y s t e m .................................................................... General. The Cuddapah system ; lithology of the Cuddapahs ; absence of fossils in the Cuddapahs ; classification of the system. Distribution. The Lower Cuddapah ; the Delhi system ; Bijawar series ; the Cheyair and Gwalior series. The Upper Cuddapahs; the Nallamalai, Kaladgi, Kistna, etc., series. Economics. Stratigraphic position of the Cuddapahs. References. CHAPTER VI -

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T he G o n d w a n a S y stem

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Extent and thickness; rocks; structural features. Life during the Vindhyan period. Classification. Distribution of the Low'er Vindhyan ; Semri series ; the Kurnool series, Malani series, etc. Meaning of “ Lower ” and “ U pper” Vindhyan. The distribution of the Upper Vindhyan. Vindhyan sandstones. Economics of the system. The Himalayan Vindhyans. The relation of the Himalayan unfossiliferous systems to the Peninsular Puranas. Homotaxis of the Vindhyan system. References.

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The Cambrian of India, (i) The Salt-Range. The principal geological features of the range. The Cambrian of the Salt-Range ; the purple sand­ stone , the Neobolus beds; magnesian sandstone. Salt-pseudomorph shales, (ii) The Spiti area—the Spiti geosyncline. The Cambrian of S p iti; Haimanta system ; Cambrian fossils. Autoclastic conglomerates. The Cambrian of Kashmir. References.

S il u r ia n , D e v o n ia n a n d L o w er Ca r b o n ife r o u s S y s t e m s ..........................................................................................

General, (i) The Spiti area ; the Silurian ; the Devonian Mu th series ; the Carboniferous—Lipak and Po series ; the Upper Carboniferous uncon­ formity. Table of Palaeozoic systems in Spiti. (ii) Kashmir area, (iii)

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The Middle Gondwanas: rocks; the Panchet series; the Pachmarhi or Mahadev series ; Maleri series; Parsora series; Triassic age of the Middle Gondwanas. The Upper Gondwanas : distribution ; lithology ; the Rajmahal series ; the Rajmahal flora; Satpura and Central Pro­ vinces ; Jabalpur stage; Godavari area ; Kota stage ; Gondwanas of the East Coast; Rajahmundri, Ongole and Madras outcrops; the Upper Gondwanas of Cutch. Umia series. Economics. References. CHAPTER XI

U p p e r C a r b o n if e r o u s a n d P e r m ia n S y s t e m s

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The commencement of the Aryan e ra ; the Himalayan geosyncline; the nature of geosynclines. Upper Carboniferous and Permian of India. (i) Upper Carboniferous and Permian of the Salt-Range. Boulder-bed ; Speckled sandstone; Productus limestone; Productus fauna. The Anthracolithic systems, (ii) Upper Carboniferous and Permian of the Himalayas. The Permo-Carboniferous of Spiti. Productus shales. Kashmir; H azara; Simla; Burma. Marine beds of Umaria. References. CHAPTER X II T he T ria ssic S ystem

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General. The principles of classification of the geological record ; the view of Professors Chamberlin and Salisbury, (i) The Trias of Spiti. The zonal classification of the system ; Triassic fauna, (ii) Hazara, (iii) The Trias of the Salt-Range—the Ceratite beds, (iv) Baluchistan, (v) B urm a; Napeng series, (vi) Kashmir. References.

CHAPTER VIII The

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CHAPTER X

CHAPTER VII T h e Ca m b r ia n S y s t e m

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General. The ancient Gondwanaland ; Lemuria ; the Gondwana system of India ; the geotectonic relations of the Gondwana rocks ; their fluviatile nature ; evidences of changes of clim ate; ’organic remains in the Gondwana rocks ; distribution of the Gondwana rocks ; classification of the system. The Lower Gondwana: Talchir series; Talchir fossils ; the Damuda series ; igneous rocks of the Damuda coal-measures ; effects of contact-metamorphism; the Damuda flora; Damuda series of other areas. Homotaxis of the Damuda and Talchir series. Economics. Classification.

T he G o n d w a n a S ystem {Continued)

CHAPTER V

T h e V in d h y a n S y st e m

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CHAPTER X III T h e J u r a s s ic S y s t e m

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Instances of Jurassic development in India. Life during the Jurassio P®ri°d. (i) Jura of the Central Himalayas ; the Kioto limestone ; Spiti shales ; the fauna of the Spiti shales. Mt. Everest region. The Tal series of the Outer Himalayas, (ii) Juras of Baluchistan, (iii) Hazara ; the

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CONTENTS

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CON TENTS

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Spiti shales of Hazara, (iv) Burma—Namyau beds, (v) Juras of the SaltRange. Marine transgressions during the Jurassic period ; the nature of marine transgressions, (vi) The Jurassics of Cutch—Patcham, Chari, Katrol and Umia series, (vii) Rajputana—Jaisalmer limestone. Refer­ ences. CHAPTER XIV

and Baluchistan, (ii) Salt-Range. (iii) Kohat. (iv) Potwar. (v) Hazara.

(vi) Kashmir, (vii) The Outer Himalayas; Subathu series, (viii) Assam ; economic utility of the Assam Eoccno rocks, (ix) Burma; Eocene mammals. References. CHAPTER XIX

T h e Cr e ta c eo u s S y s t e m .................................................................... 192

T he O lig o c e n e a n d L o w e r M io c e n e S y s t e m s

Varied facies of the Cretaceous of India, the geography of India during the Cretaceous period, (i) Cretaceous of S p iti; Giumal sandstone ; Chikkim scries; Flysch. (ii) Chitral. Plutonic and volcanic action during the Cretaceous. Etfotic blocks of Johar. (iii) Cretaceous Volcanic series of Kashmir, (iv) Hazara, (v) Cretaceous of Sind and Baluchistan; Hippurite limestone; Parh limestone ; Pab sandstone. Cardita beaumonti beds, (vi) Salt-Range. (vii) Assam, (viii) Burma. References.

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Oligocene ; restricted occurrence, (i) Baluchistan, (ii) Sind; Nari series. (iii) Assam, (iv) Burma ; Pegu series : petroleum, origin, mode of occur­ rence, gas, migration ; petroleum areas in India. Lower Miocene, (i) Sind; GaJ series; Bugti beds. (ii) Salt-Range, Potwar, Jam m u ; Murree series, (iii) Outer Himalayas, (iv) Assam; Surma series, (v) B urm a; Upper Pegu series. Igneous action. Change in conditions. References.

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CHAPTER XV T h e Cr eta ceo us S y stem ( Continued)— P e n in s u l a

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(i) Upper Cretaceous of the Coromandel coast; geological interest of the S.E. Cretaceous; the U tatur stage; Trichinopoly stage; Ariyalur stage ; Niniyur stage ; Fauna of the S.E. Cretaceous ; Utatur, Trichino­ poly, and Ariyalur faunas, (ii) The Narbada valley Cretaceous ; Bagh beds; conclusions from the fauna of the Bagh beds, (iii) Tho Lameta series or Infra-trappean beds ; metasomatic limestones. Age of the Lameta series. Cretaceous Dinosaurs of India. References.

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211 CHAPTER X XI

The great volcanic formation of India. Area of the plateau basalts ; ’ their thickness ; tho horizontality of the lava sheets ; petrology ; absence of magmatic differentiation; microscopic characters of the Deccan basalts. Stratigraphy of the Deccan Trap. Inter-trappcan beds ; a type-section. The mode of eruption of the Deccan Traps—fissure-eruption. Fissure dykes in the Traps. Age of the Deccan Traps. Economics. Re­ ferences.

T he P le ist o c e n e S ystem — G lacial A ge in I n d ia

T h e T e r t ia r y S y stem s — I n t r o d u c t o r y

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General. Physical changes a t the commencement of the Tertiary era. Tho elevation of the Himalayas ; three phases of upheaval of the Him­ alayas. Distribution of the Tertiary systems in India : Peninsula ; extraPeninsula. Dual facies of Tertiary deposits. Geography of India during early Tertiary, (i) Tertiaries of Surat and Broach, (ii) Kathiawar. Dwarka beds, Perim Island Tertiary, (iii) Tertiaries of Cutch. (iv) Rajputana. (v) The Coromandel coast—Cuddalore series, (vi) Travancore. Tertiary systems of the extra-Peninsular India, (i) Sind. Table of formations. (ii) Salt-Range. Table of formations, (iii) Himalayas—Kashmir Him­ alayas and Punjab and Kumaon Himalayas. Tertiaries of Inner Himalayas, (iv) Assam, (v) Burma. The Tertiary gulf of Burma. References. CHAPTER XVIII T h e E o cene S y s t e m .........................................................-

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CHAPTER X X II T h e P l e i s t o c e n e S y s t e m ( Continued)— T h e I n d o - G a n g e t ic A l l u v i u m .......................................................................................... 282 The plains of India. Nature of the Indo-Gangetic depression. Extent and thickness of the alluvial deposits. Changes in Rivers. Lithology. Classification; Bhangar; Khadar. The Ganges delta, the Indus delta. Economics. The Rajputana desert; composition of tho desert sand ; the origin of the Rajputana desert. The Rann of Cutch. References. CHAPTER X X III T h e P l e i s t o c e n e S y s t e m (Continued)— L a t e r i t e

240 Kirthar (i) Sind

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The Pleistocene or Glacial Age of Europe and America. A modified Pleis­ tocene Glacial Age in India. The nature of the evidence for an Ice Age in India ; Dr. Blanford’s views. Ice Age in tho Himalayas ; Physical re­ cords. The extinction of tho Siwalik mammals—one further evidence. Interglacial periods. References.

CHAPTER XVII

Ranikot series; Fossils of the Ranikot series. Laki series. series ; Nummulitic limestone ; Fossils of the Kirthar series,

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General. The nature of the Siwalik deposits. Geotectonic relations of the Siwaliks. Tho “ Main Boundary ” Fault. The real nature of the “ Main Boundary ” F a u lt; Middlemiss’s views. The Palaeontological interest of the Siwalik system. Evolution of the Siwalik fauna; migra­ tions into India. Lithology; mode of formation of the Siwaliks in the Gangetic trough. Classification. Siwalik fauna; fossil anthropoid apes. Age of Siwalik system. Parallel series of deposits. References.

CHAPTER XVI D eccan T r a p

CHAPTER XX T he S iw a l ik S y stem — M id d l e M io c en e to L o w er P l e is to cene ............................................................................................

Laterite a regolith peculiar to India. Composition of laterite ; its distribu­ tion. High-level laterite and low-level laterite. Theories of the origin of Jatente, recent views; secondary changes in laterite; resilicification. xne age of laterite. Economics. References.

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CO NTENTS

CONTENTS

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CHAPTER XXIV

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CHAPTER XXVII (APPENDIX)

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PA G E

P l e ist o c e n e a n d R e c e n t ( Continued)

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Examples of Pleistocene and Recent deposits. Ossiferous alluvium of the Upper Sutlej ; of the Tapti and Narbada. The Karewas of Kashmir. Porbander stone. Sand-dunes; Teris. Loess deposits. The Potwar fiuvio-glacial deposits. Cave-deposits. Regur or black cotton-soil; the origin of Regur. The “ Daman ” slopes. The Human epoch. References.

CHAPTER XXV

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P h y sio g r a p h y Principles of physiography illustrated by the Indian region. Mountains : tho structure of the Himalayas ; recent ideas ; the tectonic zones ; cause of the syntaxial bends of the Himalayas ; the mountains of the Peninsula. Plateaus and plains : plateau of volcanic accumulation ; plateau of erosion. Valleys : the valley of Kashmir a tectonic valley ; erosion-valleys ; valleys of the Himalayas ; the transverse gorges ; configuration of the Himalayan valleys ; valleys of the Peninsula. Basins or lakes : func­ tions of lakes; types of lakes; Indian examples. The Coast-lines of India. References. CHAPTER XXVI E conomic G eo lo gy General. Water ; wells, springs, artesian wells; Thermal and Mineral Springs. Clay ; china-clay, terra-cotta, fire-clay, fuller’s earth. Sands ; glass-sand. Lime ; cements ; mortar ; composition of cements ; produc­ tion. Building-stones ; granites; limestones; marbles, serpentine; sandstones, Vindhyan sandstones, Gondwana sandstones ; laterite, slates, traps. Coal; production in India ; Gondwana coal; Tertiary coal. Peat. Petroleum ; Burma, Assam, N.W. In d ia ; natural gas. Metals and ores ; views of Sir T. H. Holland. Gold : its occurrence ; production of vein-gold; alluvial gold. Copper; the copper-ores of Sikkim. Iron ; its occurrence on a vast scale ; economic value ; production ; its distri­ bution. Manganese; distribution of manganese in the geological for­ mations of India ; production ; uses. Aluminium ; bauxite in laterite ; economic value of Indian bauxite ; uses. Lead ; lead-ores of Bawdwin ; production. Silver and zinc. Tin ; the tin-ore of Mergui and Tavoy. W olfram; wolfram of Tavoy ; uses of tungsten. Chromium; occurrence; uses. Antimony ; arsenic ; cobalt and nickel; zinc. Precious and semi­ precious stones. Diamonds ; Panna and Golconda diamonds. Rubies and sapphires ; Burma rubies ; sapphires of Kashmir. Spinel. Jadeite ; occurrence; formation. B eryl; emeralds and aquamarines. Chrysoberyl. Garnets. Zircon. Tourmalines. Other gem-stones of India. Agate3, rock-crystal, amethyst. Amber. Economic mineral products. S a lt; sources of Indian s a lt; Rock-salt Mines ; other salts. Saltpetre or nitre. Mode of occurrence of nitre ; its production ; uses. Alum. Borax. Reh salts ; the origin of reh efflorescence. Mica ; uses of mica ; micadeposits of Nellore and Hazaribagh. Corundum ; occurrence ; distribu­ tion ; uses: other abrasives; millstones, grindstones. Kyanite and Sillimanite. Beryl. Monazite; its occurrence; uses. G raphite; its occurrence ; uses. Steatite ; mode of origin of steatite. Gypsum. Mag­ nesite ; occurrence of magnesite. Asbestos. Barytes. Fluor-spar. Phosphatic deposits. Mineral paints. Uranium minerals ; pitchblende of Gaya. Titanium. Vanadium. Rare minerals. Pyrite and sulphur; uses cf sulphur. Soils, soil-formation ; the soils of India.

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G eology of K ash m ir

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General. Physical features of Kashmir ; the chief orographic features. The Outer ranges; their simple geological structure; the “ duns ” . The Middle ranges; the Panjal range; “ orthoclinal ” structure of the Middle ranges. The Inner ranges ; physical aspects of the zone of highest elevation. The valleys; transverse gorges; their configuration. The lakes. Glaciers ; transverse and longitudinal types of glaciers. Records of tho Pleistocene Ice Age. The Stratigraphy of Kashmir. Introduc­ tion. Comparative stratigraphy of Simla and Hazara areas. Table of the geological formations. The Archaean and pre-Cambrian systems ; petrology; distribution. Salkhala series. The Palaeozoic group. Out­ crops. The Cambrian. The Ordovician. D istribution; composition. The Silurian. D istribution; rocks, fossils. The Devonian. Occur­ rence ; petrology. The Lower Carboniferous—Syringothyris limestone series. Distribution; Lower Carboniferous fossils. The Middle Car­ boniferous—Fenestella shales ; passage beds ; distribution ; lithology; fauna ; age of the Fenestella series. The mid-Palaeozoic unconformity of N.W. Kashmir and Hazara ; the Tanawal series. The Upper Carboniferous ■—Panjal Volcanic series. Middle Carboniferous earth-movements. Physical history at the end of tho Dravidian era. Panjal volcanic series ; distribution ; nature of the Panjal agglomerate slates ; Panjal lavas ; petrology ; age and extension of the Panjal lavas. Inter-trappean lime­ stones. Lower Gondwana beds— Gangamopteris beds ; distribution ; lithology; the Golabgarh section; fossils; age. The Permian; Zewan series ; fossils ; ago of the Zewan series. Permo-Carboniferous inliers in the Sub-Himalayas of Jammu. Krol Series. Tho Triassic; Trias of Kashmir, wide distribution ; lithology ; Lower Trias ; Middle Trias ; Upper Trias. Relations of the Kashmir and Spiti provinces during the UpporTrias. The Jurassic ; the Jurassic of Ladakh; Jurassic of Banihal. Tho Cretaceous; Chikkim series of Rupshu-Zanskar. Cretaceous volcanics of Astor, Burzil and Dras. The Tertiary ; Introductory ; Indus Valley Tertiaries; Tertiaries of the Jammu hills. The Subathu series of Jammu and the Pir Panjal. The Murree series. The Siwalik system ; Lower, Middle and Upper Siwaliks. Pleistocene and Recent; Karewas. Relation of Karewas to Glacial and Inter-Glacial periods. Later deposits. Geotectonic Features of the N.W. Himalayas. In d e x

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LIST OF ILLUSTRATIONS (1) PLATES PA G E

PLATE

facing page 14 Alukthang Glacier 16 Snout of Sona Glacier from Sona 28 Mud Volcano—one of the largest—Minbu, Burma 64 Bellary Granite, Gneiss Country, Hampi Banded Porphyritic Gneiss (Younger Archaean), Nakta Nala, Chhindwara District . . . . . . . „ 66 VI. “ Marble Rocks ” (Dolomite Marble), Jabalpur . . . „ 76 VII. Upper Rewah Sandstone, Rahutgarh,Sangor District „ 94 VIII. Overfolding of the Palacozoic Rocks, Upper Lidar Valley, Central H i m a l a y a s ....................................................... , , 1 1 4 IX . Reversed Fault in Carboniferous Rocks, Lebung Pass, Central H im a la y a s ..........................................................................„ 116 X. Barrier of Coal across Kararia Nala . . . . . „ 132 XI. Contorted Carboniferous Limestone . . . . . „ 160 X II. Folded Trias Beds, Dhauli Ganga Valley,Central Himalayas „ 166 X III. Geological Map of Lidar Valley. Silurian-Trias Sequence in K a s h m i r ..........................................................................At end of book XIV. Plan of Vihi District, Kashmir XV. Geological Map of the Pir Panjal XVI. Sketch Map of the Himalayan Geosyncline and its Relation to adjacent Mountain-systems of Central Asia ,, „ XVII. Tectonic Sketch Map of the Garhwal Himalayas „ „ XVIII. Geological Sketch Map of the Syntaxial Bend of the NorthWest Himalayas XIX. Geological Map of Hazara XX. Geological Map of India I. n. III. IV. V.

(2) IN THE TEXT F IG .

1. Diagrammatic Section through the Himalayas to show their relations to the Tibetan Plateau and the Plains of I n d i a ..................................... 5 2. Barren Island Volcano in the Bay of Bengal . . . . . . 3. Diagram showing Contortion in the Archaean Gneiss of Bangalore 4. Section across the Aravalli Range to the Vindhyan Plateau showing the peneplaned synclinorium of the most ancient mountain range of India 5. Section across the Singhbhum Anticlinorium, Chota Nagpur . . . ■ iagram showing the Relation of Dharwar Schists with the Gneisses g ®ecti°n illustrating the Relation of Cuddapah and Kurnool Rocks action showing Relation between Gwalior Series and Rocks of the Vindh­ yan System

26 56 75 79 83 87 98

XX

L IS T O F IL L U S T R A T IO N S

FIG.

9. Section illustrating the General Structure of the Salt-Range (Block-faults). Section over Chambal Hill ( E a s t ) ....................................................... 10. Section across tho Dandot scarp from Khewra to Gandhala, Salt-Range 11. Section along the Parahio River, S p i t i ....................................................... 12. Section of Palaeozoic Systems of N. Shan States (Burma), Section across the Nam-tu Valley a t L i l u ................................................................. 13. Sketch Map of typical Gondwana Outcrop . . . . . . 14. Tectonic Relations of the Gondwana Rocks. . . . . . . 15. Sketch Map of the Gondwana Rocks of the Satpura Area . . . 16. Generalised Section through the Gondwana Basin of tho Satpura Region 17. Section from Dhodha Wahan across the western part of Mt. Sakcsar, SaltRange ..................................................................................................... 18. Section across tho Salt-Range, western part, showing the Upper Palaeo­ zoic and Mesozoic s y s t e m s ................................................................. 19. Section of the Carbon-Trias Sequence in the Tibetan Zone of the Himalayas ( S p i t i ) ..................................................................................................... 20. Palaeozoic Rocks of the N. Shan States . . . . . . . 21. Section of the Trias of S p i t i .......................................................................... 22. Diagrammatic Section of Mt. Sirban, Abbottabad, Hazara . . . 23. Continuation of preceding Section further South-East to the Taumi Peak 24. Section through the Bakh Ravine from Musa Khel to Nammal 25. Section of the Jurassic and Cretaceous Rocks of Hundes . . . . 26. Sketch Section in the Chichali P a s s ................................................................. 27. View of Deccan Trap C o u n try .......................................................................... 28. Section of Nummulitic Limestone Cliffs; Salt Range . . . . 29. Section across the Potwar G e o s y n c lin e ........................................................ 30. Diagrams to illustrate the Formation of Reversed Faults in the Siwalik Zone of the Outer H im a l a y a s ................................................................. 31. Section to illustrate the Relations of the Outer Himalayas to the Older Rocks of the Mid-Himalayas (Kumaon Himalayas) . . . . 32. Section across the Sub-Himalayan Zone east of the Ganges River 33. Diagrammatic section across the Indo-Gangetic Synclinorium 34. Diagrammatic section across the Kashmir Himalaya, showing the broad Tectonic F e a t u r e s ................................................................................... 35. Section through the Simla H i m a l a y a ........................................................ 36. Section across Western Rajputana to illustrate the peneplanation of an ancient mountain c h a i n .......................................................................... 37. View of the great Baltoro G l a c i e r ........................................................ 38. Section of Pir Panjal across the N.E. Slope from Nilnag—Tatakuti 39. General Section, Naubug Valley, Margan Pass and Wardwan, to show the disposition of tho Palaeozoic rocks of K a s h m ir ..................................... 40. Section across Lidar Valley A n t i c l i n e ........................................................ 41. Section of tho Zewan Series, Guryul Ravine. . . . . . 42. Section of the Triassic System of K a s h m i r .............................................. 43. Section showing the Relation of the Permo-Carboniferous and Eocene of the Jammu H i l l s ................................................................................... 44. Section across the Outermost Hills of the Sub-Himalaya at Jammu 45. Diagrammatic representation of the nappe structure of Garhwal Himalaya

paqr

104 105

113 117 127 128 137 139 150 152 160 164 170 172 173 174 178 185 212

243 257 264 266 267 284 315 316 319 390 391 400 400 417 421 432 439 441

CHAPTER I PHYSICAL FEATURES

B efo r e commcncing the study of the stratigraphical, i.e. historical, geology of India, it is necessary to acquire some knowledge of the principal physical features. The student should make himself familiar with the main aspects of its geography, the broad facts regarding its external relief or contours, its mountain-systems, plateaus and plains, its drainage-courses, its glaciers, volcanoes, etc. This study, with the help of physical or geographical maps, is indis­ pensable. Such a foundation-knowledge of the physical facts of the country will not only be of much interest in itself, but the student will soon find that the physiography of India is in many respects corre­ lated to, and is, indeed, an expression of, its geological structure and history. Geological divisions of India—The most salient fact with regard to both the physical geography and geology of the Indian region is that it is composed of three distinct units or earth-features, which are as unlike in their physical as in their geological characters. The first two of these three divisions of India have a fundamental basis, and the distinctive characters of each, as we shall see in the following pages, were impressed upon it from a very early period of its geological history, since which date each area has pursued its own career inde­ pendently. These three divisions are : 1. The triangular plateau of the Peninsula {i.e. the Deccan, south of the Yindhyas), with the island of Ceylon. 2. The mountainous region of the Himalayas which borders India to the west, north, and east, including the countries of Afghanistan, Baluchistan, and the hill-tracts of Burma, known as the extrapeninsula. 3. The great Indo-Gangetic Plain of the Punjab and Bengal, separating the two former areas, and extending from the valley of the Indus in Sind to that of the Brahmaputra in Assam. Their characters and peculiarities—As mentioned above, the Penuisula, as an earth-feature, is entirely unlike the extra-Peninsula. W.Q.I.

A

2

GEOLOGY OF IN D IA

Tile following differences summarise the main points of divergence between these two regions : The first is stratigraphic, or that con­ nected with the geological history of the areas. Ever since the dawn of geological history (Cambrian period), the Peninsula has been a land area, a continental fragment of the earth’s surface, which since that epoch in earth-history has never been submerged beneath the sea, except temporarily and locally. No considerable marine sediment of later age than Cambrian was ever deposited in the interior of this land-mass. The extra-Peninsula, on the other hand, has been a region which has lain under the sea for the greater part of its history, and has been covered by successive marine deposits characteristic of all the great geological periods, commencing with the earliest, Cambrian. The second difference is geoteclonic, 'or pertaining to the geological structure of the two regions. The Peninsula of India reveals quite a different type of architecture of the earth’s crust from th at shown by the extra-Peninsula. Peninsular India is a segment of the earth’s outer shell th at is composed in great part of generally horizontally reposing rock-beds that stand upon a firm and immovable foundation and that have, for an immense number of ages, remained so—impas­ sive amid all the revolutions that have again and again changed the face of the earth. Lateral thrusts and mountain-building forces have had but little effect in folding or displacing its originally horizontal strata. The Deccan is, however, subject to one kind of structural dis­ turbance, viz., fracturing of the crust in blocks, due to tension or compression. The extra-Peninsula, on the contrary, is a portion of what appears to have been a comparatively weak and flexible portion of the earth’s circumference that has undergone a great deal of crumpling and deformation. Rock-folds, faults, thrust-planes, and other evidences, of movements within the earth are ^observed in this region on an extensive scale, and they point to its being a portion of the earth that has undergone, at a late geological epoch, an enormous amount of compression and upheaval. The strata everywhere show high angles of dip, a closely packed system of folds, and other violent departures from their original primitive structure. The third difference is the diversity in the physiography of the two areas. The difference in the externa 1or surface relief of Peninsular and extra-Peninsular India arises out of the two above-mentioned dif­ ferences, as a direct consequence. In the Peninsula, the mountains are mostly of the “ relict ” type, i.e. they arc not mountains in the true sense of the term, but are mere outstanding portions of the old

PH Y SIC A L F E A T U R E S

3

plateau of the Peninsula that have escaped, for one reason or another, the weathering of ages that has cut out all the surrounding parts of the land ; they are, so to say, huge “ tors ” or blocks of the old plateau. Its rivers have flat, shallow valleys, with low imperceptible gradients, because of their channels having approached to the baselevel of erosion. Contrasted with these, the mountains of the other area are all true mountains, being what are called “ tectonic ” moun­ tains, i.e. those which owe their origin to a distinct uplift in the earth’s crust and, as a consequence, have their strike, or line of extension, more or less conformable to the axis of th at uplift. The rivers of this area are rapid torrential streams, which are still in a very youthful or immature stage of river development, and are continuously at work in cutting down the inequalities in their courses and degrading or lowering their channels. Their eroding powers are always active, and they have cut deep gorges and precipitous canons, several thousands of feet in depth, through the mountains in the mountainous part of their track. Types of the earth’s crust exemplified by these divisions—The type of crust segments of which the Peninsula is an example, is known as a Horst—a solid crust-block which has remained a stable land-mass of 'great rigidity, and has been unaffected by any folding movement generated within the earth during the later geological periods. The only structural disturbances to which these parts have been suscept­ ible are of the nature of vertical, downward or upward, movements of large segments within it, between vertical (radial) fissures or faults. The Peninsula has often experienced this “ block-movement ” at various periods of its history, most notably during the Gondwana period. The earth-movements characteristic of the flexible, more yielding type of the crust, of which the extra-Peninsula is an example, are of the nature of lateral (i.e. tangential) thrusts which result in the wrinkling and folding of more or less linear zones of the earth’s sur­ face into a mountain-chain (orogenic movements). These move­ ments, though they may affect a large surface area, are solely con­ fined to the more superficial parts of the crust, and are not so deepseated as the former class of movements characteristic of horsts. Physical characters of the plains of India—The third division of ndia, the great alluvial plains of the Indus and the Ganges, though, ^ umanly speaking, of the greatest interest and importance, as being e principal theatre of Indian history, is, geologically speaking, the east interesting part of India. In the geological history of India they

GEOLOGY OF IN D IA

PH Y SIC A L F E A T U R E S

are only the annals of yester-year, being the alluvial deposits of the rivers of the Indo-Ganges systems, borne down from the Himalayas and deposited at their foot. They have covered up, underneath a deep mantle of river-clays and silts, valuable records of past ages, which might have thrown much light on the physical histojy of the Peninsular and the Himalayan areas, and revealed their former con­ nection with each other. These plains were originally a deep depres­ sion or furrow lying between the Peninsula and the mountain-region. With regard to the origin of this great depression there is some dif­ ference of opinion. The eminent geologist, Eduard Suess, thought it was a “ Fore-deep ” fronting the Himalayan earth-waves, a “ sag­ ging ” or subsidence of the northern part of the Peninsula, as it arrested the southward advance of the mountain-waves. Colonel Sir S. Burrard, from some anomalies in the observations of the deflec­ tions of the plumb-line, and other geodetic considerations, has sug­ gested quite a different view.1 He thinks that the Indo-Gangetic alluvium conceals a great deep rift, or fracture, in the earth’s subcrust, several thousand feet deep, the hollow being subsequently filled up by detrital deposits. He ascribes to such sub-crustal cracks or rifts a fundamental importance in geotectonics, and attributes the elevation of the Himalayan chain to an incidental bending or curling movement of the northern wall of the fissure. Such sunken tracts be­ tween parallel, vertical dislocations are called “ Rift-Valleys ” in geology. The geologists of the Indian Geological Survey have not accepted this view of the origin of the Indo-Gangetic depression.2 Rajputana a debatable area—The large tract of low country, form­ ing Rajputana, west of the Aravallis, possesses a mingling of the dis­ tinctive characters of the Peninsula, with those of the extra-Peninsula, and hence cannot with certainty be referred to either. Rajputana can be regarded as a part of the Peninsula inasmuch as in geotectonic characters it shows very little disturbance, while in its containing marine, fossiliferous deposits of Mesozoic and Cainozoic ages it shows greater resemblance to the extra-Peninsular area. In this country, long-continued aridity has resulted in the establishment of a desert topography, buried under a thick mantle of sands disintegrated from the subjacent rocks as well as blown in from the western sea-coast and from the Indus basin. The area is cut off from the water-

of the rest of the Indian continent, except for occasional storms of rain, by the absence of any high range to intercept the moisture-bearing south-west monsoons which pass directly over its expanse. The desert conditions are hence accentuated with time, the water-action of the internal drainage of the country being too feeble to transport to the sea the growing mass of sands. There is a tradition, supported by some physical evidence, that the basin of the Indus was not always separated from the Peninsula by the long stretch of sandy waste as at present. “ Over a vast space of the now desert country, east of the Indus, traces of ancient river-beds testify to the gradual desiccation of a once fertile region; and throughout the deltaic flats of the Indus may still be seen old channels which once conducted its waters to the Rann of Cutch, giving life and prosperity to the past cities of the delta, which have left no living records of the countless generations that once inhabited them.” 1

4

L 1 The Origin of the, Himalayas, 1912 (Survey of India Publication). Presidential AA ddress, tlie Indian Science Congress, Lucknow, 1916. I 2 See Dr. Hayden, Relationship of the Himalaya to the Indo-Gangetic Plain and [the Indian Peninsula, liec. G.S.I. vol. xliii. pt. 2, 1913, and R. D. Oldham, Mem, K .S .I. vol .xlii. pt. 2, 1917.

5

c irc u la tio n

MOUNTAINS The Himalayan mountains—The mountain-ranges of the extraPeninsula have had their origin in a series of earth-movements which

F10- 1.—Diagrammatic section through the Himalayas to show their relations to the Tibetan Plateau and the plains of India. * Watershed of the Himalayas. (Vertical scale greatly exaggerated.)

proceeded from outside India. The great horst of the Peninsula, composed of old crystalline rocks, has played a large part in the his­ tory of mountain-building movements in Northern India. I t has united the extent, and to some degree controlled the form of the c lef ranges. Broadly speaking, the origin of the Himalayan chain, , e naost dominant of them all, is to be referred to powerful lateral rusts acting from the north or Tibetan direction towards the 1 Sir T. H. Holdich, Imperial Gazetteer, vol. i.

GEOLOGY OF IN D IA

PH Y SIC A L F E A T U R E S

Peninsula of India. These thrusting movements resulted in the pro­ duction of fold after fold of the earth’s crust, pressing against the Peninsula. The curved form of the Himalayas1 is due to this resist­ ance offered by the Peninsular “ foreland ” to the southward advance of these crust-waves, aided in some measure by two other minor obstacles—an old pene-plained mountain-chain like the Aravalli mountains to the north-west and the Assam ranges to the north-east.2 {The general configuration of the Himalayan chain, its north-west south-east trend, the abrupt steep border which it presents to the plains of India with the much more gentle slope towards the opposite or Tibetan side, are all features which are best explained, on the above view, as having been due to the resistances the mountainmaking forces had to contend against in the Peninsula and in the two other hill-ranges. The convex side of a mountain range is, in general, in the opposite direction to the side from which the thrusts are directed, and is the one which shows the greatest amount of plication, fracture, and overthrust. This is actually the case with the outer or convex side of the Himalayas, in which the most characteristic struc­ tural feature is the existence of a number of parallel, reversed faults, or thrust-planes. The most prominent of this system of thrusts, the outermost, can be traced from the Punjab Himalayas all through the entire length of the mountains to their extremity in eastern Assam. This great fault or fracture is known as the Main Boundary Fault. Physical features of the Himalayas—The geography of a large part of the Himalayas is not known, because immense areas within it have not yet been explored by scientists ; much therefore remains for future observation to add to (or alter in) our existing knowledge. Lately, however, the Mt. Everest and other expeditions to Tibet and the Karakoram have made additions to our knowledge of large tracts of Himalayas. The eastern (Assam) section of the Himalayas, how­ ever, is geographically still almost a terra incognita. The Himalayas are not a single continuous chain or range of mountains, but a series of several more or less parallel, or converging ranges, intersected by enormous valleys and extensive plateaus. Their width is between 100 and 250 miles, comprising many minor ranges, and the length of the Central axial range, the “ Great Himalaya range ”, is 1500 miles. The individual ranges generally present a steep slope towards the

-plains of India and a more gently inclined siope towards Tibet. The northern slopes are, again, clothed with a thick dense growth of forest vegetation, surmounted higher up by never-ending snows, while the southern slopes are too precipitous and bare cither to accumulate the snows or support, except in the valley basins, any but a thin sparse jungle. The connecting link between the Himalayas and the other high ranges of Central Asia—the Hindu Kush, the Karakoram, the K u e n Lun, the Tien Shan and the Trans-Alai ranges—is the great mass of the Pamir, “ the roof of the world.” The Pamirs (Persian P(fi-mir = foot of the eminences) are a series of broad, alluviumfilled valleys, over 12,000 feet high, separated by linear mountainmasses, rising to 17,000 feet. From the Pamirs to the south­ east, the Himalayas extend as an unbroken wall of snow-covered mountains, pierced by passes, few of which are less than 17,000 feet in elevation. The Eastern Himalayas of Nepal and Sikkim rise very abruptly from the plains of Bengal and Oudh, and suddenly attain their great elevation above the snow-line within strikingly short dis­ tances from the foot of the mountains. Thus, the peaks of Kanchenjunga and Everest are only a few miles from the plains and are visible to their inhabitants. But the Western Himalayas of the Punjab and Kumaon rise gradually from the plains by the intervention of many ranges of lesser altitudes, their peaks of everlasting snows are more than a hundred miles distant, hidden from view by the mid-Himalayan ranges to the inhabitants of the plains. / Meteorological influence of the Himalayas—This mighty range of mountains exercises as dominating an influence over the meteoro­ logical conditions of India as over its physical geography, vitally affecting both its air and water circulation. Its high snowy ranges have a moderating influence on the temperature and humidity of Northern India. By reason of its altitude and its situation directly in the path of the monsoons, it is most favourably conditioned for the precipitation of much of their contained moisture, either as rain or snow. Glaciers of enormous magnitude are nourished on the higher ranges by this precipitation, which, together with the abundant rain­ fall of the lower ranges, feed a number of rivers, which course down to the plains in hundreds of fertilising streams. In this manner the Himalayas protect India from the gradual desiccation which is overspreading the Central Asian continent, from Tibet north­ wards, and the desert conditions that inevitably follow continental desiccation. Limits of the Himalayas—Geographically, the Himalayas are

6

1 From Sanskrit, Him Alaya, meaning the abode of snow. I 2 Another view is th at the curvature is the result of the interference of similar fold­ in g movements proceeding from the Iranian or the Hindu Kush system of mountains. (See page 314.)

7

8

GEOLOGY OF IN D IA

to terminate, to the north-west, at the great bend of. the Indus, where it cuts through the Kashmir Himalayas, while the south­ eastern extremity is defined by the similar bend of the Brahmaputra in upper Assam. At these points also there is a well-marked bending of the strike of the mountains from the general north-west—south-east, to approximately north and south direction. Some geographers have refused to accept this limitation of the Himalayan mountain system, because according to them it ignores the essential physical unity of the hill-ranges beyond the Indus and the Brahmaputra with the Himalayas. They would extend the term Himalayas to all those ranges to the east and west {i.e. the Hazara and Baluchistan moun­ tains and some ranges of Burma) which originated in the same great system of Pliocene orogenic upheavals. /

P H Y SIC A L F E A T U R E S

9

g e n e ra lly c o n s id e re d

y v The Syntaxial Bends of the Himalayas—The trend-line of the Himalayan chain and its east and west terminations possess much interest from a structural point of view and need further remarks. For 1500 miles from Assam to Kashmir, the chain follows one persistent S.E.-N.W. direction and then appears to terminate suddenly at one of the greatest eminences on its axis, Nanga Parbat (26,620), just where the Indus has cut an extra­ ordinarily deep gorge right across the chain. Geological studies have shown that just at this point the strike of the mountains bends sharply to the south and then to the south-west, passing through Chilas and Hazara, instead of pursuing its nortS-westerly course through Chitral. All the geological formations here take a sharp hair-pin bend as if they were bent round a pivotal point obstructing them. This extraordinary inflexion affects the whole breadth of the mountains from the foot-hills of Jhelum to the Pamirs. On the west of this syntaxis (as this acutely reflexed bundle of mountain-foMs is termed) the Himalayan strike swings from the prevalent N.E. to a N.-to-S. direction in Hazara and continues so to Gilgit; then it turns E.-to-W., the Pamirs showing a distinct equatorial disposition of their geological formations. To the south-east of this, the main tectonic strike quickly takes on a N.W.-S.E. orientation through Astor and Deosai—a direction which persists with but minor departures to eastern Assam. The eastern limit of the Himalayas beyond Assam is yet not quite cer­ tain, but from the few geographical and geological observations that have been made in this region it appears that the tectonic strike here also under­ goes a deep knee-bend from an easterly to a southerly trend. In the Arakan Yomas the geological axis of the mountains for several hundred miles is meridional, bending acutely to the N.E. near Fort Hertz. Beyond this point there is an abrupt swing to the N.W., then to E.N.E.-W.S.W. and finally to E.-W. through Assam and Sikkim. The cause of these remarkable bends of the mountain-axis is discussed on page 314.1 1 D. N. Wadia ; The Syntaxis of the N.W. Himalayas: its Rocks, Tectonics and Orogeny. Records O.S.I., vol. lxv. pt. 2, 1931.

Classification of the Himalayan Range (I.) Geographical—For geographical purposes Burrard has divided the long alignment of the Himalayan system into four sections : the Punjab Himalayas, from the Indus to the Sutlej, 350 miles long ; Kumaon Himalayas, from the Sutlej to the Kali, 200 miles long; Nepal Himalayas, from the Kali to the Tista, 500 miles long ; and Assam Himalayas, from the Tista to the Brahmaputra, 450 miles long. Also the Himalayan system is classified into three parallel or longi­ tudinal zones, each differing from one another in well-marked orographical features : (1) The Great Himalaya : the innermost line of high ranges, rising above the limit of perpetual snow. Their average height extends to 20,000fe e t; on it are situated the peaks, like Mount Everest, K2, Kanchenjunga, Dhaulagiri, Nanga Parbat, Gasherbrum, Gosainthan, Nanda Devi,1 etc. (2) The Lesser Himalayas, or the middle ranges : a series of ranges closely related to the former but of lower elevation ; seldom rising much above 12,000-15,000 feet. The Lesser Himalayas form an intricate system of ranges ; their average width is fifty miles. (3) The Outer Himalayas, or the Siwalik ranges, which intervene between the Lesser Himalayas and the plains. Their width varies from five to thirty miles. They form a system of low foot-hills with an average height of 3000-4000 feet. v^n.) Geological—As regards geological structure and age the Himalayas fall into three broad stratigraphical belts or zones. These zones do not correspond to the geographical zones as a rule. (1) The Northern or Tibetan Zone, lying behind the line of highest elevation {i.e. the central axis corresponding to the Great Himalaya). This zone is composed of a continuous series of highly fossiliferous marine sedimentary rocks, ranging in age from the earliest Palaeozoic \ to the Eocene age. Except near the north-western extremity (in * 1 Mount Everest K2 Kanchenjunga Dhaulagiri Nanga Parbat Gasherbrum Gosainthan Nanda Devi Rakaposhi Namcha Barwa Badri Nath Gangotri -

- Nepal Himalaya - Karakoram - Nepal Himalaya

„

-

Kashmir Himalaya Karakoram Nepal Himalaya Kumaon Himalaya . Kailas range Assam Himalaya Kumaon Himalaya -

. -

29,002 ft. 28,250 9f 28,146 ,, 26,795 99 26,620 9f 26,470 26.291 99 25,645 99 25,550 y> 25,445 55 23,190 55 21,700 55

GEOLOGY OF IN D IA

PH Y SIC A L F E A T U R E S

Hazara and Kashmir) rocks belonging to this zone are not known to occur south of the line of snowy peaks. (2) The Central or Himalayan Zone, comprising most of the Lesser or Middle Himalayas together with the Great Himalaya. I t is mostly composed of crystalline and metamorphic rocks—granites, gneisses, and schists, with unfossiliferous sedimentary deposits of very ancient (Purana) age. (3) The Outer or Sub-Himalayan Zone, corresponding to the Siwalik ranges, and composed entirely of Tertiary, and principally of Upper Tertiary, sedimentary river-deposits. The above is a very brief account of a most important subject in the geography of India, and the student must refer to the works men­ tioned at the end of the chapter for further information, especially to that by Sir Sidney Burrard and Sir Henry Hayden, Second Edition, 1932, revised by Burrard and Dr. A. M. Heron, which contains the most luminous account of the geography and the geology of the Himalayas. Other ranges of the extra-Peninsula—Running transversely to the strike of the Himalayas at either of its extremities, and believed to belong to the same system of upheaval, are the other minor mountainranges of extra-Peninsular India. Those to the west are the flanking ranges which form the Irdo-Afghan and Indo-Baluchistan frontier. Those to the east are the mountain-ranges of Burma. Many of these ranges have an approximate north-to-south trend. The names of these important ranges are :

of the Peninsula are : The Aravalli mountains, the Vindhyas, Sat­ puras, the Western Ghats (or, as they are known in Sanskrit, the Sahvadris), and the irregular broken and discontinuous chain of ele­ vations known as the Eastern Ghats. Of these, the Aravallis are the only instance of a true tectonic mountain-chain, all the others (with one possible exception to be mentioned below) are merely mountains of circumdenudation, i.e. they are the outstanding remnants, or out­ liers, of the old plateau of the Peninsula that have escaped the de­ nudation of ages. Not one of them shows any axis of upheaval that is coincident with their present strike. Their strata show an almost undisturbed horizontality, or, at most, very low angles of dip. The Aravallis were a prominent feature in the old Palaeozoic and Mesozoic geography of India, and extended as a continuous chain of lofty mountains from the Deccan to possibly beyond the northern limit of India. What we at present see of them are but the deeply eroded remnants of these mountains, their mere stumps laid bare by repeated cycles of erosion. Vindhya mountains. Satpura range—The rocky country which rises gradually from the south of the Gangetic plains culminates in the highlands of Central India, comprising Indore, Bhopal, Bundelkhand, etc. The southern edge of this country is a steep line of prominent escarpments which constitute the Vindhyan mountains, and their easterly continuation, the Kaimur range. Their elevation is between 2500 and 4000 feet above the sea-level. The Vindhyas are for the most part composed of horizontally bedded sedimentary rocks of ancient age, the contemporaries of the Torridon sandstone of Scotland. South of the Vindhyas, and roughly parallel with their direction, are the Satpura mountains. The name Satpura, meaning “ seven folds ”, refers to the many parallel ridges of these mountains. The chain of ridges commences from Rewah, runs south of the Narbada valley and north of the Tapti valley, and stretches westwards through the Rajpipla hills to the Western Ghats. The Vindhya and the Satpura chains form together the backbone of middle India. Very large parts of the Satpuras, both in the west and the east, are formed of bedded basalts ; the central part is composed, in addition to a cap­ ping of the traps, of a core of granitoid and metamorphic rocks, overlain by Mesozoic sandstones. Some parts of the Satpuras give proof °f having been folded and upheaved, the strike of the folding showing a rough correspondence with the general direction of the range. It is Probable, therefore, that parts of the Satpuras are, like the Aravallis, a weather-worn remnant of an old tectonic chain.

10

W e st

The The The The

Salt-Range. Suleiman range. Bugti range. Kirthar range.

E ast

The Assam ranges. The Manipur ranges. The Arakan Yoma. The Tenasserim range.

With the exception of the Salt-Range and the Assam ranges, the other mountains are all of a very simple type of mountain-structure, and do not show the complex inversions and thrust-planes met with in the Himalayas. They are again principally formed of Tertiary rocks. The Salt-Range and the Assam ranges, however, are quite different, and possess several unique features which we shall discuss later on. Their rocks have undergone a greater amount of fracture and dislocation, and they are not composed so largely of Tertiary rocks. Mountain ranges of the Peninsula—The important mountain ranges

11

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P H Y SIC A L F E A T U R E S

The Western Ghats—The greater part of the Peninsula is consti­ tuted by the Deccan plateau. I t is a central tableland, extending from 12° to 21° North Latitude, rising about 2000 feet mean elevation above the sea, and enclosed on all sides by hill-ranges. To its west are the Sahyadris, or Western Ghats, which extend unbroken to the ex­ treme south of Malabar, where they merge into the uplands of the Nilgiris, some of whose peaks rise to the altitude of 8700 feet above the sea-level (Dodabetta peak), the highest of the Peninsula. From the Nilgiris the Western Ghats extend (after the solitary opening, Palghat Gap), through the Anaimalai hills, to the extreme south of the Peninsula. The Western Ghats, as the name Ghat denotes, are, down to Malabar, steep-sided, terraced, flat-topped hills or cliffs facing the Arabian sea-coast and running with a general parallelism to it. Their mean elevation is some 3000 feet. The horizontally bedded lavas of which they are wholly composed have, on weathering, given to them a characteristic “ landing-stair ” aspect. This peculiar mode of weathering imparts to the landscapes of the whole of the Deccan a strikingly conspicuous feature. The physical aspect of the Western Ghats south of Malabar—that is, the portion comprising the Nilgiris, Anaimalai, etc.—is quite different from these square-cut, steep-sided hills of the Deccan proper. The former hills are of a more rounded and undulating outline, clothed under a great abundance of indigen­ ous, sub-tropical forest vegetation. The difference in scenery arises from the difference in geological structure and composition of the two portions of the Western Ghats. Beyond Malabar they are composed of the most ancient massive crystalline rocks, and not of horizontal layers of lava-flows. The Eastern Ghats—The broken and discontinuous line of moun­ tainous country, facing the Bay of Bengal, and known as the Eastern Ghats, has neither the unity of structure nor of outline characteristic of a mountain-chain. The component parts belong to no one geological formation, but vary with the country through which the hills pass, and the high ground is made up of several units, which are formed of the steep scarps of several of the South Indian formations. Some of these scarps are the surviving relics of ancient mountain-chains elevated contemporaneously with the Aravallis. Among the remaining, less important, hill ranges of the Peninsula are the trap-built Rajmahal hills of western Bengal; the Nallamalai hills near Cuddapah, built of gneissose granite, and the gneissic plateau of Shevaroys and Pachamalai, south-west of Madras.

GLACIERS

12

13

The snow-line, i.e. the lowest limit of perpetual snow, on the side of the Himalayas facing the plains of India, varies in altitude from about 1 4 000 feet on the eastern part of the chain to 19,000 feet on the western. On the opposite, Tibetan, side it is about 3000 feet higher, owing to the great desiccation of that region and the absence of mois­ ture in the monsoon winds that have traversed the Himalayas. In Ladakh, with a scanty snow-fall, it is 18,000 feet. In the Hindu Kush the average snow-line is 17,000 feet high. Owing to the height of the snow-line, the mountains of the Lesser Himalayas, whose general elevation is considerably within 15,000 feet, do not reach it, and therefore do not support glaciers at the present day. But in some of the ranges, e.g. the Pir Panjal, there is clear evidence, in the thick masses of moraines covering their summits and upper slopes, in the striated and polished rock-surfaces, in the presence of numerous erratics, and other evidences of mountain-sculpture by glacier-ice, such as cirques and numerous small lake-basins, th at these ranges were extensively glaciated at a late geological period, corresponding with the Pleistocene Glacial age of Europe and America. Glaciers of the Himalayas—The Great Himalaya, or the innermost line of ranges of high altitudes reaching beyond 20,000 feet, are the enormous gathering grounds of snow which feed a multitude of glaciers, some of which are among the largest in the world outside the Polar circles. Much attention is being paid now to the scientific study and observation of the Himalayan glaciers, both by the Indian Geo­ logical Survey and by scientific explorers of other countries. Their size—In size the glaciers vary between wide limits, from those that hardly move beyond the high recesses in which they are formed, to enormous ice-flows rivalling those of the Arctic circle. The majority of the Himalayan glaciers are from two to three miles in length, but there are some giant streams of twenty-four miles and up­ wards, such as the Milam and Gangotri glaciers of Kumaon and the Zemu glacier, draining the Kanchenjunga group of peaks in Sikkim. The largest glaciers of the Indian region are those of the Karakoram, discharging into the Indus ; these are the Hispar and the Batura of the Hunza valley, 36 to 38 miles long, while the Biafo and the Baltoro glaciers of the Shigar tributary of the Indus are about 37 miles in length. Still larger are the Siachen and the Remo glaciers, falling into the Nubra affluent of the Indus, some 45 miles long, and the Fedehenko of the Pamir region of about the same dimensions. Some

measurements taken at the end of the Baltoro glacier gave a depth of 400 feet of solid ice ; the thickness in the middle of the body would be considerably greater. The thickness of ice in the Zemu stream is 650 feet, while the Fedchenko has a depth of nearly 1800 feet of ice. These giant ice-streams of the Karakoram are doubtless survivors of the last Ice age of the Himalayas, as the present day precipitation of snow in this region is not sufficient to feed these great rivers of ice. Like the dwindling glaciers of the Kuen Lun, these streams also will gradually diminish in size and retreat from continuous defect of “ alimentation ”.1 The majority of the glaciers are of the type of valley glaciers, but what are known as hanging glaciers are by no means uncommon. As a rule the- glaciers descending transversely to the strike of the mountain are shorter, more fluctuating, in their lower limits, and, since the grade is steeper, they descend to such low levels as 7000-8000 feet in some parts of the Kashmir Himalayas. Those, on the other hand, that move in longitudinal valleys, parallel to the strike of the mountains, are of a larger volume, less sensitive to alternating temperatures and seasonal variations, and, their grad­ ients being low, they rarely descend to lower levels than 10,000 feet. Limit of Himalayan glaciers—The lowest limit of descent of the glaciers is not uniform in all parts of the Himalayas. While the glaciers of Kanchenjunga in the Sikkim portion hardly move below the level of 13,000 feet altitude, and those of Kumaon and Lahoul to 12,000 feet, the glaciers of the Kashmir Himalayas descend to much lower limits, 8000 feet, not far above villages and fields. In several places recent terminal moraines are observed at so low a level as 7000 feet. A very simple cause of this variation has been suggested by T. I). La Touche. In part it is due to the decrease in latitude, from 36° in the Karakoram to 28° in the Kanchenjunga, and in part to the greater fall of the atmospheric moisture as rain and not as snow in the eastern Himalayas, which rise abruptly from the plains without the intervention of high ranges, than in the western Himalayas where, though the total precipitation is much less, it all takes place in the form of snow. Peculiarities of Himalayan glaciers—One notable peculiarity of the Himalayan glaciers, which may be considered as distinctive, is the presence of extensive superficial moraine matter, rock-waste, which almost completely covers the upper surface to such an extent that the ice is not visible for long stretches. On many of the Kashmir glaciers it is a usual thing for the shepherds to encamp in summer, with their 1 Prof. Kenneth Mason, Records G.S.I., vol. lxiii., part 2, 1930.

I.

GEOLOGY OF IN D IA

PLATE

14

P H Y SIC A L F E A T U R E S

15

flocks, on the moraines overlying the glacier ice. The englacial and sub-glacial moraine stuff is also present in such quantity as sometimes to choke the ice. The diurnal motion of the glaciers, deduced from various observations, is between three and five inches at the sides, and from eight inches to about a foot in the middle. Observations on the movement of the great Baltoro glacier by the Italian Expedition of 1909 gave as the velocity of ice at the snout the comparatively much higher figure of 5 feet 10 inches in 24 hours. The diurnal motion of the Fedchenko is about 1£ feet, while that of the Zemu is 9 inches. In many parts of the Himalayas there are local traditions, supported in many cases by physical evidence, that there is a slow, general retreat of the .glacier-cnds ; at the lower ends of most of the Himalayan glaciers there are enormous heaps of terminal moraines left behind by the retreating ends of the glaciers. The rate of diminution is variable in the different cases, and no general rule applies to all. In some cases, again, there is an undoubted advance of the glacier ends on their own terminal moraines. Professor Mason’s recent study of the Himalayan and Karakoram glaciers has given some valuable results : the velocity of glaciers and their advance and retreat depend on topo­ graphical factors and not on climatic factors ; the velocity has been found to vary in different glaciers from one inch to many feet per day ; variations in glacier activity, as indicated by movements of the snout, may be due to causes which are, in distinct cases, secular, periodic, seasonal, or accidental. Mason observes th at the Karakoram and Himalayan glaciers show no evidence whatever of any regular periodic variation corresponding with any supposed weather-cycles. In the summer months there is a good deal of melting of the ice on the surface. The water, descending by the crevasses, gives rise to a considerable amount of englacial and sub-glacial drainage. The accumulated drainage forms an englacial river, flowing through a large tunnel, the opening of which at the snout appears as an ice-cave. Records of past glaciation in the Himalayas—Large and numerous as are the glaciers and the snow-flelds of the Himalayas of the present day, they are but the withered remnants of an older and much more extensive system of ice-flows and snow-fields which once covered Tibet and the Himalayas. As mentioned already, many parts of the Himalayas bear the records of an “ Ice Age ” in comparatively recent tunes. Accumulations of moraine debris are seen on the tops and sides °f many of the ranges of the middle Himalayas, which do not support any glaciers at the present time. Terminal moraines, often covered by grass, are to be seen in the Pir Panjal at heights above 6500 feet, while

16

GEOLOGY OF IN D IA

the shapes of the ice-planed mountains and the U-shaped valleys, at times terminating at the heads in amphitheatre-like hollows (cirques) are very characteristic features of this range. Ancient moraines are seen before the snouts of existing glaciers reaching up to such low elevations as 6000 feet, or even 5000 feet. Sometimes there are grassy meadows, pointing to the remains of old silted-up glacial lakes. These facts, together with the more doubtful occurrences of what may be termed fluvio-glacial drift at much lower levels in the hills of the Punjab, lead to the inference that this part of India at least, if not the Peninsular highlands, experienced a Glacial Age in the Pleistocene period.1

PLATE II.

RIVERS AND RIVER-VALLEYS Rivers, with their tributary-systems, are the main channels of drainage of the land-surface ; they are at the same time also the chief agents of land-erosion and sculpture and the main lines for the trans­ port of the products of the waste of the land to the sea. The drainagesystems of the two regions, Peninsular and extra-Peninsular India, having had to accommodate themselves to two very widely divergent types of topography, are necessarily very different in their character. In the Peninsula the river-systems, as is obvious, are all of great anti­ quity, and consequently, by the ceaseless degradation of ages, their channels have approached the last stage of river-development, viz. the base-levelling of a continent. The valleys are broad and shallow, characteristic of the regions where vertical erosion has almost ceased, and the lateral erosion of the banks, by winds, rain, and stream, is of greater moment. In consequence of their low gradients the water has but little momentum, except in flood-time, and therefore a low carry­ ing capacity. In normal seasons they are only depositing agents, pre­ cipitating their silt in parts of their basins, alluvial banks, estuarine 1 The principal glaciers of the Himalayas : Kumaon— Sikkim — Milam - . Zemu . . . - 16 miles Kedar Nath Kanchenjunga - 10 miles Gangotri Kosa . . . Punjab (Kashmir)— Rupal . . . . Karakoram— - 10 miles Biafo Diyamir 7 miles 7 miles Hispar Sonapani Baltoro Rundun . . . - 12 miles Gasherbrum - 17 miles Punrnah . . . Chogo Lungma Riino . . . . - 25 miles Siachen - 12 miles Chong Kumdan Ba t ur a . . . - unknown Niuapin -

- 1 2 miles 9 miles - 16 miles 7 miles - 39 miles -

36 24 24 45

miles miles miles miles

(Col. K. Mason)

SNOUT OF SONA GLACIER FROM SONA. Photo. J. L. Grinhnton. (Geol. Survey of India, Records, vol. xliv.)

P H Y SIC A L F E A T U R E S

17

flats etc., while the streams flow in easy, shallow meandering valleys. Xu other words, the rivers of the Peninsula have almost base-levelled their courses, and are now in a mature or adult stage of their lifehistory. Their “ curve of erosion ” is free from irregularities of most kinds except those caused by late earth-movements, and is more or less uniform from their sources to their mouths.1 Easterly drainage of the Peninsula—One very notable peculiarity in the drainage-system of the Peninsula is the pronouncedly easterly trend of its main channels, the Western Ghats, situated so close to the west border of the Peninsula, being the water-shed. The rivers that discharge into the Bay of Bengal have thus their sources, and derive their head waters almost within sight of the Arabian Sea. This fea­ ture in a land area of such antiquity as the Peninsula, where a com­ plete hydrographic system has been in existence for a vast length of geologic time, is quite anomalous, and several hypotheses have been put forward to account for it. One supposition regards this fact as an indication that the present Peninsula is the remaining half of a land mass, which had the Ghats very near its centre as its primeval water­ shed. This water-shed has persisted, while a great extension of the country west of it has been submerged underneath the Arabian Sea. Another view, equally probable, is suggested by the exceptional be­ haviour of the Narbada and the Tapti. These rivers discharge their drainage to the west, while all the chief rivers of the country, from Cape Comorin through the Western Ghats and the Aravallis to the Siwalik hills near Hard war (a long water-shed of 1700 miles), all run to the east. This exceptional circumstance is explained by the sup­ position that the Narbada and Tapti do not flow in valleys of their own eroding, but have usurped for their channels two fault-planes, or deep alluvium-filled rifts in the rocks, running parallel with the Vindhyas. These faults are said to have originated with the bending °r sagging ” of the northern part of the Peninsula at the time of the be said, however, th at the channels are wholly free from all irregularities, hf‘sf °JUe m show very abrupt irregularities of the nature of Falls. Among the u nov^n waterfalls of South India are : the Sivasamudram falls of the Cauvery in nainp1^ ’ TiT td ^ave a height of about 300 fe e t; the Gokak falls of the river of that the fall0 f district, which are 180 feet in height; the “ Dhurandhar ” or volume8 f Narbada a t Jabalpur, in which, though the fall is only 30 feet, the India arp *ar8e- The most impressive and best-known of tho waterfalls of is precinif le, ersoPPa falls of the river Sharavati in North Kanara, where the river The Yenna f i?Verf a l®dge of the Western Ghats to a depth of 850 feet in one single fall, the falls ()f t i p ?.* t ^e. Mahableshwar hills descend 600 feet below in one leap, while over the m * rain the Nilgiri hills descend less steeply in a series of five cataracts Eristic of p^ISS1C Prec'ip>ee. Indeed, it may be said that such falls are more characdi.sturb-1nr.r>eni,L S U . ^ a n °f extra-Peninsular India and bear evidence to some minor w q i es ln a k te geological age. for ^ cani*°t

B

GEOLOGY OF IN D IA

PH Y SIC A L F E A T U R E S

upheaval of the Himalayas as described before. As an accompani­ ment of the same disturbance, the Peninsular block, south of the cracks, tilted slightly eastwards, causing the eastern drainage of the area. This peculiarity of the hydrography of the Peninsula is illustrated in the distribution and extent of the alluvial margin on the two coasts. There is but a scanty margin of alluvial deposit on the western coast, except in Gujarat, whereas there is a wide belt of river-borne alluvium on the east coast, in addition to the great deltaic deposits a t the mouths of the Mahanadi, Godavari, Kistna, Cauvery, etc. A further peculiarity of the coast is the absence of deltaic deposits a t the mouths of the streams, even of the large rivers Narbada and Tapti. This peculiarity arises from the fact that the force of the cur­ rents generated by the monsoon gales and the tides is too great to allow alluvial spits or bars—the skeleton of the deltas—to accumulate. On the other hand, the debouchures of these streams are broad deep estuaries daily swept by the recurring tides. As a contrast to the drainage of Peninsular India, it should be noted that the island of Ceylon has a “ radial ” drainage, i.e. the rivers of the island flow outwards in all directions from its central highlands, as is well seen in any map of Ceylon.

channels, although certainly working at an accelerated rate, by reason of the great stimulus imparted to them by the uplift of the region near their source. The great momentum acquired by this upheaval was expended in eroding their channels at a faster rate. Thus the eleva­ tion of the mountains and the erosion of the valleys proceeded, pari passu, and the two processes keeping pace with one another to the end a mountain-chain emerged, with a completely developed valleysystem intersecting it in deep transverse gorges or can ons. These long, deep precipitous gorges of the Himalayas, cutting right through the line of its highest elevations, are the most characteristic features of its geography, and are at once the best-marked results, as they are the clearest proofs, of the inconsequent drainage of this region. From the above peculiarities the Himalayan drainage is spoken of as an ante­ cedent drainage, meaning thereby a system of drainage in which the main channels of flow were in existence before the present freatures of the region were impressed on it. The Himalayan water-shed—This circumstance of the antecedent drainage also gives an explanation of the much-noted peculiarity of several of the great Himalayan rivers, e.g. the Indus, Sutlej, Bhagirathi, Alaknanda, Kali, Karnali, Gandak, Kosi and the Brahma­ putra, that they drain not only the southern slopes of those moun­ tains, but, to a large extent, the northern Tibetan slopes as well, the water-shed of the chain being not along its line of highest peaks, but a great distance to the north of it. This, of course, follows from what we have said in the last paragraph. The drainage of the northern slopes flows for a time in longitudinal valleys, in structural troughs parallel to the mountains, but sooner or later the rivers invariably take an acute bend and descend to the plains of India by cutting across the mountain in the manner already described. The transverse gorges of the Himalayas—These transverse gorges of the Himalayas are sometimes thousands of feet in depth from the crest of their bordering precipices to the level of the water at their ottom. The most remarkable example is the Indus valley in Gilgit, W ere one place the river flows through a narrow defile, between enormous precipices nearly 20,000 feet in altitude, while the bed of the va ey is only 3000 feet above its level at Haiderabad (the head of its etfh ^ ves Sorge the stupendous depth of 17,000 feet, from r Ct eVery ^ i s chasm is carved by the river is clear sand b ° sma^ Patetes or Cfcerraces ” of river gravel and the I A S 018 °^servecl various elevations above the present bed of us>marking the successive levels of its bed. Other examples

18

J

The Drainage of the Extra-Peninsula Area

The Himalayan system of drainage not a consequent drainage—In the extra-Peninsula the drainage system, owing to the mountainbuilding movement of the late Tertiary age, is of much more recent development, and differs radically in its main features and functions from that of the Peninsula. The rivers here are not only eroding and transporting agents but are also depositing agents during their journey across the plains to the sea. Thus they have built the vast plains of North India out of a part of the silt they have removed from the mountains. The most important fact to be realised regarding the drainage is that it is not in a large measure a consequent drainage, i.e. its formation was not consequent upon the physical features, or the relief, of the country, as we now see them ; but there are clear evidences to show that the principal rivers of the area were of an age anterior to them. In other words, many of the great Himalayan rivers are older than the mountains they traverse. During the slow process of mountain-formation by the folding, contortion, and up­ heaval of the rock-beds, the old rivers kept very much to their own

19

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GEOLOGY OF IN D IA

of similar gorges are numerous, e.g. those of the Sutlej, Gandak, Kosi, Alaknanda, etc., are deep defiles of from 6000 to 12,000 feet depth and only from 6 to 18 miles width between the summits of the mountains on the sides. [Although there is not much doubt, now, regarding the true origin of the transverse gorges of the Himalayas by the process described above, these valleys have given rise to much discussion in the past, it being not admitted by some observers that those deep defiles could have been entirely due to the erosive powers of the streams that now occupy them. It was thought by many that originally they were a series of transverse fissures or faults in the mountains which have been subsequently widened by water-action. Another view was that the elevation of the Himalayas dammed back the old rivers and converted them into lakes for the time being. The waters of these lakes on overflowing have cut the gorges across the mountains, in the manner of retreating waterfalls. The absence of lacustrine deposits at the head of the principal rivers does not lend support to this view, though it is probable that this factor may have operated in a secondary way in some cases. The defile of the Alaknanda again, is known to have carved a part of its valley along a line of fault. There is no doubt, however, that some of these transverse valleys, namely those of the minor rivers, have been produced in a great measure by the process of head-erosion, by the combined action of the stream or the glacier at the head of the river pushing itself forward into the mountains, whereby the water-shed receded further and further northwards. It is necessary to suppose this because the volume of drainage from the northern slopes, in the early stages of valley-growth, could not have been large enough to give it sufficient erosive energy to keep its valleys open during the successive uplifts of the mountains.] River capture or piracy—Many of the Himalayan rivers, in their higher courses, illustrate the phenomena of river-capture or “ piracy This has happened oftentimes through the rapid head-erosion of their main transverse streams, capturing or “ beheading ” successively the secondary laterals belonging to the Tibetan drainage-system on the northern slopes of the Himalayas. The best examples of rivercapture are furnished by the Bhagirathi and other tributaries of the Ganges, the Arun in the Everest area, the Tista of Sikkim, and the Sind 1 river in Kashmir. “ Hanging valleys ” of Sikkim—Some of the valleys of the Sikkim and Kashmir Himalayas furnish instructive examples of “ hanging valleys ”, that is, side-valleys or tributaries whose level is some hun­ dreds or thousands of feet higher than the level of the main stream into which they discharge. These hanging valleys have in the majority of instances originated by the above process of rapid head1 Oldham, Rec. O.S.I. vol. xxxi. pt. 3, 1904.

P H Y SIC A L F E A T U R E S

21

• n and capture of the lateral streams on the opposite slope. A E l-k n o w n example is that of a former tributary of the Tista river of 3'kkim discharging its waters by precipitous cascades into the Rathong Chu, which is flowing nearly 2000 feet below its bed. Prof. Garwood, in describing this phenomenon, suggests that the difference in level between the hanging side-valley and the main river is due not wholly to the more active erosion of the latter, but also to the recent occupation of the hanging valley by glaciers, which have protected it from the effects of river-erosion. LAKES Lakes play very little part in the drainage system of India. Even in the mountainous regions of the extra-Peninsula, particularly in the Himalayas, where one might expect them to be of frequent occur­ rence, lakes of any notable size are very few. Lakes of Tibet, Kumaon and Kashmir—The principal lakes of the extra-Peninsula are those of Tibet (including the sacred Manasarovar and Rakas Tal, the reputed source of the Indus, Sutlej, and Ganges of Hindu traditions but which have now been proved to be the source of the Sutlej river). The Manasarovar, 200 sq. miles in area and Rakas Tal, 140 sq. miles, are fresh-water lakes, while Gunchu Tso, 30 miles to the east, is a saline lake, 15 miles long, it being a closed basin with­ out any outlet. Other examples are : the lakes of Sikkim, Yamdok Cho, 45 miles in circumference ; Chamtodong, 54 miles ; the group of small Kumaon lakes (the Nainital, Bhim Tal, etc.) ; and the few lakes of Kashmir, of which the Pangkong, Tsomoriri, the Salt Lake, the Wular and Dal are the best-known surviving instances. There is some controversy with regard to the origin of the numerous lakes of Tibet, which occupy thousands of square miles of its surface and are the recipients of its inland surface drainage. Many are regarded as due to the damming up of the main river-valleys by the alluvial fans of tributary side-valleys (F. Drew) ; 1 some are regarded as due to an elevation of a portion of the river-bed at a rate faster than the erosion of the stream (Oldham) ; 2 while some are regarded as true erosionhollows, scooped out by glaciers—rock-basins.3 The origin of the Kumaon lakes is yet uncertain ; while a few may be due to differ­ ential earth-movements like faulting, others may have been produced 1 Jammu and Kashmir Territories (London), 1875. 2 Rec. G.S.I. vol. xxi. pt. 3, 1888. 3 Huntington, Journal of Geology, vol. xiv. 1906, p. 599.

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PH Y SIC A L F E A T U R E S

GEOLOGY O F IN D IA

by landslips, glaciers, etc. The Small fresh-water lakes of Kashmir are ascribed a very simple origin by Dr. Oldham. They are regarded by him as mere inundated hollows in the alluvium of the Jhelum, like thejhils of the Ganges delta. The Manchar lake of Sind, a shallow depression, only 8-10 feet deep, but attaining an area of 200 sq. miles in the monsoon, is in all probability of like character and origin, forming a part of the drainage system of the Indus in Sind. Salinity of the Tibetan lakes—The lakes of Tibet exhibit two in­ teresting peculiarities, viz. the growing salinity of their waters and their pronounced diminution of volume, since late geological times. The former circumstance is explained by the fact that the whole lakearea of Tibet possesses no outlet for drainage. The interrupted and restricted inland drainage, therefore, accumulates in these basins and depressions of the surface where solar evaporation is very active, concentrating the chemically dissolved substances in the waters. All degrees of salinity are met with, from the drinkable waters of some lakes to those of others saturated with common salt, sodium carbonate, and borax. Their desiccation—The desiccation of the Tibetan lakes is a pheno­ menon clearly observed by all travellers in that region. Old highlevel terraces and sand and gravel beaches, 200 to 300 feet above the present level of their waters, are seen surrounding almost all the basins, and point to a period comparatively recent in geological his­ tory when the water stood at these high levels. This diminution of the volume of the water, in some cases amounting to a total extinction of the lakes, is one of the signs of the increasing dryness or desiccation of the region north of the Himalayas following a great change in its climate. This is attributed in some measure to the disappearance of the glaciers of the Ice Age, and to the uplift of the Himalayas to their present great elevation, which has cut off Tibet from the monsoonic currents from the sea. Lakes of the Peninsula—Besides the few small fresh-water lakes of the Peninsula, two occurrences there are of importance because of some exceptional circumstances connected with their origin and their present peculiarities. The one is the group of salt-lakes of Rajputana, the other is the volcanic hollow or crater-lake of Lonar in the Deccan. The Sambhar salt-lake—Of the four or five salt-lakes of Rajputana, the Sambhar lake is the most important. I t has an area of ninety square miles when full during the monsoon, at which period the depth of the water is about four feet. For the rest of the year it is dry, the surface being encrusted by a white saliferous silt. The cause of the

23

alinity of the lake was ascribed to various circumstances, to former with the Gulf of Cambay, to brine-springs, to chemical dissolution from the surrounding country, etc. But lately Sir T. H. Holland and Dr. Christie1 have discovered quite a different cause of its origin. They have proved that the salt of the Sambhar and of the other salt-lakes of Rajputana is wind-borne ; it is derived partly from the evaporation of the sea-spray from the coasts and partly from the desiccated surface of the Rann of Cutch, from which sources the dried salt-particles are carried inland by the prevalent winds. The persis­ tent south-west monsoons which blow through Rajputana for half the year, carry a large quantity of saline mud and salt-particles from the above sites, which is dropped when the velocity of the winds de­ creases. When once dropped, wind-action is not powerful enough to lift up the particles again. The occasional rainfall of these parts gathers in this salt and accumulates it in the lake-hollows which re­ ceive the drainage of the small streams. I t is calculated by these authors, after a series of experiments, th at some 130,000 tons of saline matter is annually borne by the winds in this manner to Raj­ putana during the hot weather months. . The Lonar lake—The Lonar lake is a deep crater-like hollow or basin in the basalt-plateau of the Deccan, in the district of Buldana. The depression is about 300 feet in depth and about a mile in dia­ meter. I t is surrounded on all sides by a rim formed of blocks of basalts. The depression contains at the bottom a shallow lake of saline water. The chief constituent of the salt water is sodium car­ bonate,together with a small quantity of sodium chloride. These salts arethought to have been derived from the surrounding trap country by the chemical solution of the disintegrated product of the traps and subsequent concentration. The origin of the Lonar lake hollow has been ascribed to a volcanic explosion unaccompanied by any lava eruption. This is one of the rare instances of volcanic phenomena in India within recent times. On this view the lake-hollow is an explosion-crater or a caldera. Another explanation has been given lately,2 which explains the hol­ low as due to an engulfment or subsidence produced by the sinking °f the surface between a circular fracture or fractures, into a cavern emptied by the escape of lava or volcanic vapours into the surroundIng places. c o n n e c tio n

1 Rec. O.S.I. vol. xxxviii. pt. 2, 1909. * La Touche, lice. O.S.I, vol. xli. pt. 4, 1912,

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THE COASTS The coasts of India are comparatively regular and uniform, there being but few creeks, inlets, or promontories of any magnitude. I t is only on the Malabar coast that there are seen a number of lakes, lagoons or back-waters which form a noteworthy feature of that coast. These back-waters, e.g. the Kayals of Travancore, are shallow lagoons or inlets of the sea lying parallel to the coast-line. They form an important physical as well as economic feature of the Malabar coast, affording facilities for inland water-communication. The silts brought by the recurring monsoon floods support large forests and plantations along their shores. At some places, especially along the tidal estuaries, deltaic fronts, or salt-marshes, there are the remarkable mangrove-swamps lining the coasts. The whole sea-board is sur­ rounded by a narrow submarine ledge or platform, the “ plain of marine denudation ”, where the sea is very shallow, the soundings being much less than 100 fathoms. This shelf is of greater breadth on the Malabar coast and on the Arakan coast than on the Coro­ mandel coast. From these low shelving plains the sea-bed gradually deepens, both towards the Bay of Bengal and the Arabian Sea, to a mean depth of 2000 fathoms in the former and 3000 fathoms in the latter sea. The seas are not of any great geological antiquity, both having originated in the earth-movements of the Cretaceous or early Tertiary times, as bays or arms of the Indian Ocean overspreading areas of a large southern continent (Gondwanaland), which, in the Mesozoic ages, connected India with Africa and with Australia. The coast line in front of the deltas of the Indus and Ganges is greatly changeable owing to the constant struggle between the growth of the delta and the erosion of the waves, the formation of lagoons, lakes and sand-bars. Extensive mangrove-swamps are a feature of these coasts. The coast of Sind forms part of the plain of marine denuda­ tion, with the sea hardly a few fathoms deep. It has long been the belief of geologists that the escarpment of the Western Ghats parallel with the Malabar Coast, has been formed by scarp-faulting, while Blanford considered the Mekran coast of Baluchistan to be largely shaped by an E.-W. fault. The south-east coast of Arabia and the Somaliland coast as far south as Zanzibar are likewise believed to be determined by scarp-faults. The whole of the north border of the Arabian Sea is thus surrounded by a series of steep fractures believed to be of Pliocene or even later age. The recent researches on the submarine topography of the Arabian

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gea conducted by the Murray Expedition of 1933-34 have revealed gome further interesting facts. These have shown that there are intermittent submerged ridges, 10,000 feet high, some 60 miles from the Mekran coast and parallel with it. Two parallel ridges, separated by a deep rift valley, 2000 fathoms below the surface of the sea (ex­ tension of the present valley of the Indus ?), starting from Karachi extend up to the Gulf of Oman. The axes of these ridges are probably in tectonic continuation with the Kirthar range of Sind composed of Eocene and Oligocene rocks. Colonel Sewell, the leader of the Murray Expedition, is of the opinion that there is a remarkable similarity between the topography of the floor of the Arabian Sea and the region of the great Rift Valleys of East Africa. Important geodetic data obtained by Colonel E. A. Glennie sug­ gest that the Laccadive archipelago, prolonged northwards by a chain of shoals, is on a continuation of the axes of the Aravalli moun­ tains. The islands of the seas are continental islands, with the excep­ tion of the group of coral islands, the Maldives and the Laccadives, which are atolls or barrier-reefs, reared on shallow submarine banks, the unsubmerged, elevated points of the ancient continent. Barren Island and Narcondam are volcanic islands east of the Andamans.1 The low level and smooth contours of the tract of country which lies in front of the S.E. coast below the Mahanadi suggest th at it was a submarine plain which has emerged from the waters at a comparatively late date. Behind this coastal belt are the gneissic highlands of the mainland— the Eastern Ghats—which are marked by a more varied relief and rugged topography. Between these two lies the old shore-line. The Arakan coast of the Bay of Bengal, with its numerous drowned valleys and deep inlets owes its features to recent depression. The numerous islands of this coast as well as of the Malay archipelago and the East Indies are regarded as only the unsubmerged portions of a once continuous stretch of land from Akyab to Australia. VOLCANOES Barren Island volcano—There are no living or active volcanoes any­ where in the Indian region. The Malay branch of the line of living v°lcanoes—the Sunda chain—if prolonged to the north, would conne°t a few dormant or extinct volcanoes belonging to this region. H’ j*' Seymour Sewell, Geographic and Oceanographic Research in Indian rs> Memoirs, As. Soc. Beng. vol. ix. pp. 1-7, 1935,'

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Of these the most important is the now dormant volcano of Barren Island (Fig. 2) in the Bay of Bengal, to the east of the Andaman Is­ lands, 12° 15' N. lat. ; 93° 54' E. long. W hat is now seen of it is a mere truncated remnant of a once much larger cone—its basal wreck or caldera. I t consists of an outer amphitheatre, about two miles in diameter, breached at one or two places, the remains of the old cone,

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of the island of Narcondam, a craterless volcano composed wholly of a n d e s i t i c lavas. From the amount of denudation that the cone has undergone i t appears to be an old extinct volcano. The third example is the volcano of Popa, a large centrally situated cone composed of trachytes, ashes, and volcanic breccia, situated about fifty miles north-east of the oil-field of Yenangyaung. This is also extinct now, the cone is much weathered, and the crater is only preserved in part. From the fact that some volcanic m atter is found interstratified in the s u r r o u n d i n g strata belonging to the Irrawaddy group, it seems that this volcano must have been in an active condition as far back as the Pliocene. Koh-i-Sultan—One more volcano, within the Indian Empire, but far on its western border, is the large extinct volcano of Koh-i-Sultan in the Nushki desert of western Baluchistan. There are some unverified records of a number of living and dormant volcanoes in Central Tibet and in the Kuen-Lun range of mountains to its north. None of these, however, have been proved to be active recently, although reports about the eruption of some of these having been witnessed by Tibetan travellers from a distance have been current.

Fia. 2.—The Volcano of Barren Island in the Bay of Bengal. (H. F. Blanford.)

surrounding an inner, much smaller, but symmetrical cone, composed of regularly bedded lava-sheets of comparatively recent eruption. At the summit of this newer cone is a crater, about 1000 feet above the level of the sea. But the part of the volcano seen above the waters is quite an insignificant part of its whole volume. The base of the cone lies some thousands of feet below the surface of the sea. The last time it was observed to be in eruption was early in the nineteenth century; since then it has been dormant, but sublimations of sulphur on the walls of the crater point to a mild solfataric phase into which the volcano has declined. Mr. F. R. Mallet, of the Geological Survey of India, has given a complete account of Barren Island in Memoir, vol. xxi. pt. 4, 1885.1 Narcondam. Popa—Another volcano, along the same line, is that 1 Captain Blair has described an eruption of Barren Island in 1795. Glowing cinders and volcanic blocks up to some tons in weight were discharged from the crater at the top of the new cone, which was also ejecting enormous clouds of gases and vapours. Another observer, in 1803, witnessed a series of explosions a t the crater a t intervals of every ten minutes, throwing out masses of dense black gases and vapours with great violence to considerable heights.

Among the volcanic phenomena of recent age must also be included the crateriform lake of Lonar, noticed in the preceding section. Whatever may be its exact origin, it is ultimately connected with volcanic action. Mud-Volcanoes Distribution of Mud-Volcanoes—We must here consider a curious phenomenon—what was once regarded as a decadent phase of vol­ canic action, but which has no connection whatever with vulcanicity.1 In the Irrawaddy valley and Arakan coast of Burma and the Mekran coast of Baluchistan, there occur groups of small and, more rarely, large cones of dried mud ; from small holes (“ craters ”) at the top there are discharged hydrocarbon gases (principally marsh-gas), muddy saline water, and often traces of petroleum. These conical mounds, known as mud-volcanoes, occur in great numbers in the Ramri and Cheduba islands on the Arakan coast, the majority being about twenty to thirty feet high although some are much higher. Near Minbu in Burma the cones reach about forty feet, but in the dry climate of Baluchistan some are nearly 300 feet high. The great Majority of mud-volcanoes are associated with a very gentle flow of

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muddy water, but in exceptional cases the mud-volcanoes are subject to occasional outbursts of great violence, fragments of the country rock being thrown out with force ; the friction may even be sufficient to ignite the accompanying hydrocarbon gases. Association with Petroleum—The gas, which is the prime cause of the mud-volcanoes, has the same origin as petroleum, and not only do many of the mud-volcanoes exude small quantities of petroleum, but a large number are in close proximity to small oilfields or to seepages of petroleum. Most of the mud-volcanoes are near the crests of anticlinal folds or on lines of faulting. In the Yenangyaung oilfield of Burma there have been observed veins of dried mud pene­ trating the Miocene strata ; these veins represent the channels sup­ plying mud to mud-volcanoes that have long since disappeared. The mud is derived from the disintegration of shales of Tertiary age lying beneath the surface in close association with the gas-bearing strata. Where the shale is easily disintegrated, the flow of water small, and the climate dry, the mound of dried mud will form a very conspicuous feature ; where the water brings up little mud, there may be nothing but a pool of dirty water kept in constant agitation by bubbles of gas. There are many seepages of this type in Assam, and in no case is a permanent cone formed ; in former days the brine was an important local source of salt. Mud-volcanoes are common accompaniments of petroleum occur­ rences in other parts of the world, especially in Russia and the Dutch East Indies. EARTHQUAKES The earthquake zone of India—Few earthquakes have visited the Peninsula since historic times ; but those th at have shaken the extraPeninsula form a long catalogue.1 It is a well-authenticated general­ isation th at the majority of the Indian earthquakes have originated from the great plains of India, or from their peripheral tracts. Of the great Indian earthquakes recorded in history the bestknown are : Delhi, 1720 ; Calcutta, 1737 ; Eastern Bengal and the Arakan coast, 1762 ; Cutch, 1819 ; Kashmir, 1885 ; Bengal, 1885 ; Assam, 189.7 Kangra, 1905 ; North Bihar, 1934 ; and West Baluchi­ stan, 1935 ; all of these, in the site of their origin, agree with the above statement. The area noted above is the zone of weakness and strain implied by the severe crumpling of the rock-beds in the elevation of the 1 Oldham, List of Indian Earthquakes, Mem. 0.8.1. vol. xix. pt. 3, 1883,

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Himalayas within very recent times, which has, therefore, not yet attained stability or quiescence. I t is also according to some author­ ities a belt of underload, its rocks being about 18 per cent, lighter than normal rocks. I t falls within the great earthquake belt which traverses the earth east to west. 'S T h e A ssa m E arthquake. —On the 12th June, 1897, there occurred in Assam, heralded by a roar of extraordinary loudness, one of the most disa 3trous earthquakes of the world on record ; the disturbed area bounded by the isoseismal of 5 or 6 being no less than 1,600,000 sq. miles. Shillong, with the surrounding country of 150,000 sq. miles, was laid waste in less than one minute, all communications were destroyed, the plains riddled with rents and flooded and the hill-sides were scarred by gigantic landslips. The seismic motion was a complicated undulatory movement of the ground, the vertical component of which must ha ve been hi gh, for stones on the roads of Shillong were tossed in the air “ like peas on a drum ”. The maxi­ mum amplitude of horizontal vibration was as much as 7 inches, their period being one second. Wide, gaping earth-fissures opened out in all directions in the alluvial plains, from which issued innumerable jets of water and sand, like fountains, spouting up to 3 or 4 feet in the air. Beds of rivers, taDks and even wells were ridged up, or filled, by the outpouring sand, thus greatly disturbing the drainage system of the land and causing extensive flooding. Over a wide area encircling the epicentre, the moun­ tains precipitated landslips of unusual dimensions, which further ob­ structed the drainage. The main shock was succeeded by hundreds of after-shocks during the first month, felt all over the shaken area. These shocks originated in a large number of shifting foci, scattered over the main epicentral tract in a fitful manner, certain districts registering far more shocks than others. Of great significance geologically are the concomitant structural changes produced on the surface of the ground, such as fault-scarps and fractures, local changes of level, compression of the ground, and slight changes in the heights of hills. The most important fault-scarp ran parallel with the Chidrang river for 12 miles, with a vertical throw varying from 1 to 35 feet, producing a number of water-falls and as many as thirty lakes in the course of the river. R. D. Oldham, the author of a valuable memoir on this earthquake, has stated that the complex phenomena of this quake and the occurrence of many maxima of intensity are inconsistent with a simple or single fault-dislocation. He believes that there were numerous foci, or centres of disturb­ ance, situated over a tract 200 miles long and 50 miles wide. The original disruption starting in a thrust fault initiated numerous sympathetic shocks along branch-faults. Tho after-shocks were closely connected with the subsequent movements of these faults and served in some degree to locate them. Oldham has computed the velocity of the earth-waves as about 2 miles per second and the depth of origin of the main shock at only 5 miles or even less.1 * R. D. Oldham, Memoirs, G.S.I. vol. xxix, 1899.

30

GEOLOGY OF IN D IA The K angra E arthquake. —The

earthquake took place on the early morn­ ing of the 4th April, 1905. The shock, which was felt over the whole of India north of the Tapti valley, was characterised by exceptional violence and destructiveness along two linear tracts between Kangra and Kulu, and between Mussoorie and Dehra Dun. These were the epifocal tracts. The destruction grew less and less in severity as the distance from them in­ creased, but the area that was perceptibly shaken, and which is encom­ passed by the isoseist of Intensity II, of the Rossi-Forel scale, included such distant places as Afghanistan, Quetta, Sind, Gujarat, the Tapti valley, Puri and the Ganges delta. The centra or the foci of the original concus­ sion, or blow, were linear, corresponding to the two linear epicentra, Kangra-Kulu and Mussoorie-Dehra Dun, or areas which were directly over­ head and in which the vibrations had a large vertical component. The isoseists , or curves of equal intensity, were hence ellipsoidal. *• The velocity of the quake was difficult to judge, because of the absence of any accurate time-records at the different outlying places. But from a number of observations, the mean is deduced to be nearly 1-92 miles per second as the velocity of the earth-wave. Middlemiss does not support the view that earthquakes of great severity originate near the surface in a complex network of faults and fractures. He ascribes to the present earthquake a deep-seated origin, and calculates, from Dutton’s formula for deducing the depth of focus, a depth varying from 21 to 40 miles. The main-shock was sudden, with only a few premonitory warnings, but the after-shocks, of moderate to slight intensity, which succeeded it for weeks and months, were several hundred in number. During the whole of 1906 the number of after-shocks was from ten to thirty a month. In 1907 they decreased in number, but scarcely in intensity. In the succeeding years the number of shocks grew fewer till they gradually disappeared. The geological effects of the earthquake were not very marked. There were £he usual disturbances of streams, springs, and canals ; a number of landslips and rock-falls took place, also a few slight alterations in the level of some stations and hill-tops {e.g. Dehra Dun and the Siwalik hills showed a rise of about a foot relatively to Mussoorie). No true fissures of disloca­ tions were, however, seen. In the above respects this earthquake offers a marked contrast to the Assam quake of 1897, where the geological results were of a more serious description and more permanent in their effect. With regard to the cause of the earthquake, there is no doubt that it was a tectonic quake. Middlemiss is of opinion that it was due to a slipping of one of the walls or change of strain of a fault parallel to the “ Main Boundary Fault ” of the outer Himalayas at two points. Just where the two epi­ centra lie are two very well-defined “ bays ” or inpushings of the younger Tertiary rocks into the older rocks of the Himalayas, showing much packing and folding of the strata. Relief was sought from this compression by a slight sinking of one side of the fault.1 The B ih a r E arthquake. —On the afternoon of 15th January, 1934, North Bihar and Nepal were shaken by an earthquake of high intensity. Within 1 Memoirs G.S.I. vol. xxxviii., 1910.

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three minutes the cities of Monghyr and Bhatgaon (Nepal) were in ruins and t wns so far apart as Kathmandu, Patna and Darjeeling were strewn with debris of many public and private buildings. Houses in Pumea and Sitaarhi tilted and sank under the ground and sand and water were emitted from countless fissures in the ground opened on either side of the Ganges. The intensity of the main shock was so great that the recording apparatus of the majority of the seismographs were thrown out of action, while the shocks were recorded, at seismological stations so far away as Pasadena, Leningrad and Tokyo. The area enveloped by the Isoseist of Intensity II was roughly 1,900,000 sq. miles. The main epicentra, where the intensity r e a c h e d "the degree of X, were three: (1) Motihari-Madhubani, (2) Kath­ mandu and (3) Monghyr. 11,000 sq. miles of the Ganges basin was riddled by fissures and sand-vents which ejected large volumes of water and sand flooding the cultivated country and killing the standing crops. The total loss of human life is estimated at more than 12,000. The effects of the earthquake on the general configuration and drainage of the country, alterations of level, fault-scarps, landslips, etc., were not so marked as in the Assam quake of 1897. The period and amplitude of vibrations and the maximum acceleration of the earth-wave were likewise not so remarkable. Estimates of the depth of focus on the various standard methods of cal­ culation vary largely, but it is probable that the movements responsible for the shock may have been along a highly inclined fracture or fractures. With regard to the cause, there is some agreement that this earthquake was not primarily caused by displacements along the Himalayan Boundary Faults or thrusts, but that a more probable source of disturbance lay in the folded and fractured zone of the crust underneath the Gangctic Basin—a geosynclinal depression the bottom of which must conceivably be under great strain.1 W est Baluchistan (Quetta) Earthquake.—This seismic disaster, though rather local in incidence, brought unusual destruction of life and property on the town of Quetta on the night of 31st May, 1935. In a few moments this large military station was converted into a graveyard entombing 20,000 people. The epicentral tract is calculated to be only about 68 miles long and 16 miles broad, between Quetta and Kalat, away from which the intensity of damage rapidly decreased. The area over which the shock was felt, enclosed by Isoseist of Intensity IV and V, was 10,000 sq. miles, which, considering the extraordinary destruction caused at the epicentre, is unusually small. From this fact, as also from the one that the intensity °f the quake, as judged by the distribution of the damage, fell off rapidly from the epicentre, it is evident that the focus of origin of this earthquake could not be very deep-seated. Extensive rock-falls took place from the limestone cliffs around Quetta and the ground, where composed of alluvium or loose soil, was fissured by a Network of cracks. There were however no marked upheavals on the sides ^ e cracks, which were mainly superficial. 1 Records G.S.I. vol. Ixviii. pt. 2, 1934. A memoir on the subject is under publica-

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GEOLOGY OF IN D IA

The earthquake was of the tectonic kind, though no connection has been established between this (or the less severe previous quake of 1931), and the various faults that have been noted in this region of severely com­ pressed and looped fold-axes. The mountains of the" Quetta region form a deep re-entrant angle, their tectonic axes being as it were festooned around a pivot near Quetta. The strain on the rock-folds arising from such a structure is probably responsible for the well-known seismic instability of this part of Baluchistan.1 Local Alterations of Level Elevation of the Peninsular tableland—Few hypogene disturbances have interfered with the stability of the Peninsula as a continental land-mass for an immense length, of geological time, but there have been a few minor movements of secular upheaval and depression along the coasts within past as wTell as recent times. Of these, the most important is that connected with the slight but appreciable elevation of the Peninsula, exposing portions of the plain of marine denudation as a shelf or platform round its coasts, the west as well as the east. Raised beaches are found at altitudes varying from 100 to 150 feet at many places round the coasts of India ; a common type of raised beach ,is the littoral concrete, composed of an agglutinated mass of gravel, sand with shells and coral fragments ; while marine shells are found at several places some distance inland, and a t a height far above the level of the tides. The steep face of the Sahyadri mountains, looking like a line of sea-cliffs, and their approximate parallelism to the coast lead to the inference that the escarpment is a result of a recent elevation of the Ghats from the sea and subsequent sea-action modified by subaerial denudation. Marine and estuarine deposits of post-Tertiary age are met with on a large scale towards the southern extremity of the Peninsula. Local alterations—Besides these evidences of a rather prominent uplift of the Peninsula, there are also proofs of minor, more local alterations of level, both of elevation and depression, within subrecent and pre-historic times. The existence of beds of lignite and peat in the Ganges delta, the peat deposits below the surface near Pondicherry, the submerged forest discovered on the eastern coast of the island of Bombay, etc., are proofs of slow movements of depression. Evidences of upheaval arc furnished by the exposure of some coral reefs along the coasts, low-level raised beaches on various parts of the Ghats, and recent marine accumulations above the present level of the sea. 1 W. D. West, Records G.S.I. vol. Ixix. pt. 2, 1935, and Memoirs G.S.I. vol. lxvii. pt. 1, 1934.

33

Submerged forest of Bombay. Alterations of level in Cutch—The ubmerged forest of Bombay is nearly 12 feet below low-water mark 30 feet below high-water; here a number of tree-stumps are seen with their roots in situ, embedded in the old soil.1 On the Tinnevelli coast a similar forest or fragment of the old land surface, half an acre in extent, is seen slightly below high-water mark. Further evi­ dence to the same effect is supplied by the thick bed of lignite found at Pondicherry, 240 feet below ground level, and the layers of vegetable debris in the Ganges delta. About twenty miles from the coast of Mekran the sea deepens suddenly to a great hollow\ This is thought to be due to the submergence of a cliff formerly lying on the coast. The recent subsidence, in 1819, of the western border of the Rann of Cutch under the sea, accompanied with the elevation of a large tract of land (the Allah Bund), is the most striking event of its kind recorded in India, and was witnessed by the whole population of the country. Here an extent of the country, some 2000 square miles in area, was suddenly depressed to a depth of from 12 to 15 feet, and the whole tract converted into an inland sea. The fort of Sindree, which stood on the shores, the scene of many a battle recorded in history, was also sub­ merged underneath the waters, and only a single turret of that fort remained, for many years, exposed above the sea. As an accompani­ ment of the same movements, another area, about GOO square miles, was simultaneously elevated several feet above the plains, into a mound which was appropriately designated by the people the “ Allah Bund ” (built of God). The elevated tract of land, knowm as the Madhupur jungle, near Dacca, is believed to have been upheaved as much as 100 feet in quite recent times. This upheaval caused the deflection of the Brahmaputra river eastward into Sylhet, away from the Ganges valley. Since this change the Brahmaputra has again gradually changed its bed to the west. Even within historic times the Rann of Cutch was a gulf of the sea, with surrounding coast towns, a few recognisable relics of which yet exist. The gulf was gradually silted up, a process aided no doubt by a slow elevation of its floor, and eventually converted into a low-lying tract of land, which at the present day is alternately a dry saline desert for a part of the year, and a shallow swamp for the other part. The branching^'onfe, or deep, narrow inlets of the sea, in the Andaman and Nicobar islands in the Bay of Bengal, point to a submergence of these islands within late geological times, by which its inland valleys were “ drowned ” in their lower parts. Good examples of drowned

w.a.i.

1 Rec. O.S.I. vol. xi. pt. 4, 1878.

c

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GEOLOGY OF IN D IA

valleys occur on the Arakan coast, which, with its numerous estuaries and inlets proceeding inland from a submarine shelf, gives proof of recent submergence along the whole stretch of country from Akyab to the Dutch East Indies. In some of the creeks of Kathiawar near Forbander, on the other hand, oyster-shells were found at several places and at levels much above the present height of the tides, while barnacles and serpulae were found at levels not now reached by the highest tides. In Sind a number of oyster-banks have been seen several feet above high-water mark. Oyster-shells discovered lately at Calcutta likewise point to a slight local rise of the eastern coast. Himalayas yet in a state of tension—I t is the belief of some geologists that appreciable changes of level have recently taken place, and are still taking place, in the Himalayas, and that although the loftiest mountains of the world, they have not yet attained to their maximum elevation, but are still rising. That alterations of level have lately taken place is clear from a number of circumstances. Many of the rivers bear incontrovertible proofs of recent rejuvenation, due to the uplift of their water-shed. Another fact, suggesting the same inference, is the frequency and violence of earthquakes on the Him­ alayas and in the depressed tract lying at their foot. By far the largest number of disastrous Indian earthquakes have occurred, as already remarked, along these tracts. They indicate that the strata under the Himalayas are in a state of tension, and are not yet settled down to their equilibrium plane. Relief is therefore sought by the subsidence of some tracts and the elevation of others. ISOSTASY India is particularly favourably circumstanced for the study of geodesy (the science of surveying and measuring large areas of the earth). Its triangular shape provides, from the foot of the Himalayas to Cape Comorin, a stretch of 1700 miles of land over one meridian. Again the deformation of the geoid (the shape, or as it is called, the figure of the earth) in India is such that in no other part of the world has the direction of gravity been found to undergo such abnormal variations as have been detected by the Survey of India in Northern India and by the Russian surveyors north of the Pamirs in Ferghana. According to Burrard, in no other country in the world does a surface of liquid at rest deviate so much from the horizontal. I t was in India that it was discovered that a deficiency of m atter underlies the vast

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*le of superficial matter, the Himalayas ; that, on the other hand, a rhain of dense matter runs hidden to the south of the Indo-Gangetic olains; and that sea-ward deflections of the pendulum, rather than to­ wards the Ghats, prevail round the coasts of Deccan. These discover­ ies led to the formulation of the theory of mountain compensation in about 1854 by the Rev. J. H. Pratt, Archdeacon of Calcutta, a theory which was subsequently elaborated and expanded into the doctrine of Isostasy. This simple hypothesis, which has had a great vogue, par­ ticularly in America, implies a certain amount of hydrostatic balance between the different segments of the earth’s crust and an adjust­ ment between the surface topographic relief and the arrangement of density in the sub-crust, so that above each region of less density there will be a bulge, while over tracts of greater density there will be a hollow—the former will be the continents, plateaus and mountains, the latter the ocean-basins. The excess of material over portions of the earth above the sea-level will thus be compensated for by a defect of density in the underlying material, the continents and mountains being floated because they are composed of relatively light material. Similarly the floor of the ocean will be depressed because it is com­ posed of unusually dense rocky substratum. If an extra load is im­ posed on any part of the surface, e.g. ice-sheets during a glacial epoch, it must sink under it, while regions exposed to prolonged denudation must rise until equilibrium is established. The depth at which isostatic compensation is supposed to be complete is found, in the United States of America, to be about 76 miles (113*7 km.). In India it is difficult to arrive at any such definite figure, for isostatic condi­ tions must evidently be different in the Peninsula, a region of high geological antiquity, from those of the extra-Peninsular mountain region, which have undergone very recent orographic movements of the crust. In the former area isostatic balance must be more perfect than in the Himalayas. Plumb-line and pendulum observations at Dehra Dun have shown that the “ topographic deflection ”, i.e. that due to the calculated visible mass of the Himalayas to the north is 86", but the true observed deflection is only 31*. For Murree the figures are 45" and 12" re­ spectively ; while for Kaliana, near Meerut, which is only 50 miles from the foot of the Himalayas, the observed deflection is only 1", whereas it ought to be 58". These observations prove that the imalayas are largely compensated ; though not fully, for the diferences between the observed deflections and the theoretical, even Under the assumption of isostatic compensation, are too great. The

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outer and middle Himalayas are found to be under-compensated, while the central ranges appear to be over-compensated. On the Indo-Gangetic plains the deflections are invariably to the south and not towards the Himalayas. This southerly deflection increases till the Lat. 23° N., to the south of which the plumb-line deflects to the north. These discrepant data have been explained by Burrard by assuming that there exists underneath the plains a chain of dense rock, from Orissa north-westwards through Jubblepore to Kalat an assumption which is borne out by gravity measurements of recent years. Although measurements of gravity and deviations of the vertical, as carried out by the geodetic survey of India during the last two decades, broadly confirm the main postulates of the theory of isostasy, this theory is found to be inadequate in explaining the large anomalies of gravity which exist in India, even when there are no surface features present to account for them. For the main relief features of India, although a certain degree of compensation does exist, there are serious anomalies between the theoretical and observed values of the direction and force of gravity, which remain to be accounted for. For instance, the gravimetric surveys have definitely proved belts of excess of density and of defects of density in North India which are not represented by any surface deeps or heights. An alternative hypothesis of sub-crustal warping was propounded1 lately to account for these anomalies, but the subject is still in the stage of discus­ sion. It appears that India as a whole is an area of defective density. Gravity in India is in deficit by an amount of material that is measured approxi­ mately by a stratum of rock 600 feet in thickness, spread over an area of two million square miles. DENUDATION Monsoonic alternations—Among the physical features of India, a brief notice of the various denudational processes in operation in the country at the present time must be included. Inasmuch as climate is an important determining factor in the denudation of a region, the peculiar features which the climate of India possesses require con­ sideration. The most unique feature in the meteorology of India is the monsoonic alternations of wet and dry weather. The division of the year into a wet half, from May to October, the period of the moist, vapour-laden winds from the south-west (from the Bay of Bengal and the Arabian Sea) towards Tibet and the heated tracts to the north, and the dry half, from November to April, the period of the retreating 1 E. A. Glennie, Gravity Anomalies and the Structure of the Earth's Crust (Dehra Dun. 1932).

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dry winds blowing from the north-east, has a preponderating influeliCe on the character and rate of subaerial denudation of the surface o f the country. Lateritic regolith—The intensity of the influence exercised by this dominating factor in the atmospheric circulation of the Indian region will be realised when the extent and thickness of the peculiar surface formation, laterite, is considered. Laterite is a form of regolith highly peculiar to India, which covers the whole expanse of the Peninsula from the Ganges valley to Cape Comorin ; it is believed by most authorities to have resulted from the subaerial alteration of its surface rocks under the alternately dry and humid (i.e. monsoonic) weather of India. Other characteristic products of weathering of the surface rocks insitu in the Peninsula are the red soil of Madras and that capping the gneissic tracts of the Deccan generally, and the Black Soil (regur),1 which covers also large tracts of country in South India. The Reh efflorescences of the plains of North India and the formation of nitre in some soils should also be noted in this connection.2 General character of denudation sub-tropical. Desert-erosion in Rajputana—If this factor is excluded, the general atmospheric weathering or denudation of India is th at characteristic of the tropical or sub-tropical zone of the earth. This, however, is a very general statement of the case. Within the borders of India every variety of climate is met with, from the torrid heat of the vast inland plains of the Punjab and North-east Baluchistan and upland plateaus (like Ladakh) to the Arctic cold of the higher ranges of the Him alayas; and from the reeking tropical forests of the coastal tracts of the Peninsula to the desertic regions of Sind, Punjab and Rajputana. Rock disintegration is the predominant process in the one area, rock decomposition in the other. The student can easily imagine the intensity of frost-action in the Himalayan highlands and the compara­ tive mildness of the other agents of erosion in th at area, such as rapid alternations of heat and cold, chemical action, etc., and the vigorous chemical and mechanical erosion of the tropical monsoon-swept parts of the Peninsula, the denudation of some parts of which partakes of the character of th at prevailing in the equatorial belt of the earth. In the desert tracts of Rajputana, Sind and Baluchistan, mechanical disintegration due to the prevalent drought with its great extremes of heat and cold, the powerful insolation and wind-action, is dominant, to the exclusion of other agents of change. In this belt the action of 1 The subject of soils of India is treated in Chap. XXVI. p. 378. * Chapter XXVI.

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the powerful summer-winds and dust-storms which blow for about two months preceding the summer, must result in the transport of vast quantities of fine detritus, the prolonged accumulation of which has been the cause of the widespread loess deposits of N.W. India. The transporting power of winds in the drier regions of India is enormous. Thousands of tons of dust and fine sand and silt are carried by the upper currents of winds for distances of some hundred miles and dropped where their velocity decreases. Considerable erosion of the surface and of the soil-caps results in this manner in some Punjab and Rajputana tracts. Rajputana affords a note­ worthy example of the evolution of desert topography within com­ paratively recent geological times. I t also affords excellent illustra­ tions of the geological action of winds in modifying the surfacefeatures of a country. (See Sand-dunes, SAwr lands, etc.) This change has been brought about by the great dryness that has overcome this region since Pleistocene times, leading to the intensity of aeolian action on its surface. Denudation by rivers—The geological work of Indian rivers calls for a few remarks. Some experiments by Everest prove th at the Ganges conveys annually to the Bay of Bengal, at a conservative estimate, more than 356,000,000 tons of sand and clay—an average over 900,000 tons of silt a day. There are some rivers of India whose waters are more silt-laden than those of the Ganges for many days of the year. The solid matter suspended in the Indus waters and discharged below Hyderabad, in Sind, is roughly estimated at 1,000,000 tons daily. The Brahmaputra carries down more silt than the Indus or Ganges. To the mechanically transported debris must be added the invisible amountof chemically dissolved matter in the waters of the rivers. Exact measurements of these have not been made, but analyses of average samples of river-water show that amounts of salts, e.g. the sulphate and carbonate of calcium, silica and the salts of Na, Mg, Fe, etc., re­ moved from the land to the sea in solution by a river such as the Narbada or the Jhelum run into several millions of cubic feet per annum. There are wide fluctuations in the saline contents of river waters draining different rock terrains, from less than 50 to over 400 parts per million. The salinity of the Mahanadi river rising in the region of Archaean crystalline rocks, near Cuttack, is found to amount to 86 parts in a million parts of water. Peculiarity of river-erosion in India—The Indian rivers accomplish an incredible amount of erosion during the wet half of the year, transporting to the sea an enormous load of silt, in swollen muddy

P H Y SIC A L F E A T U R E S

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streams. A stream in flood-time accomplishes a hundred times the work it performs in the normal seasons. If the same amount of rain­ fall, therefore, were evenly distributed throughout the year, the de­ nudation would be far less in amount. Their floods—The Himalayan streams and rivers are specially noted for their floods of extraordinary severity in the spring and monsoon seasons. This arises from the absence in the Indian rivers of lakes which exercise a restraining influence on the number, violence and duration of river-floods. Several of the Indus floods are noted in history, the most recent and best remembered being those of 1841 and 1858. Drew 1 gives a graphic account of the 1841 flood, when, after a period of unusual low level of the waters in the winter and spring of that year, the river, all of a sudden, descended in a black mighty torrent th at in a few minutes tore and swept away everything in its course, including a whole Sikh army that had encamped on its banks below Attock with its tents, baggage and artillery. The cause of this flood is attributed to a landslip in the narrow, gorge-like part of the river in Gilgit, which blocked up the water and converted the basin of the river above it into a lake thirty-five miles long and some hundreds of feet in depth. The sudden bursting of the barrier by the constantly increasing pressure of the water on it after the spring thaw is supposed to have caused the inundation. Many mountain channels are known to have been dammed back by the precipitation of a whole hillside across them. In 1893, in Garhwal, a tributary of the Ganges, the Alaknanda, was similarly blocked by the fall of a hillside, and was converted into a lake at Gohna. The lake spread in extent and steadily rose in height for several months, till the waters ultimately surmounted the obstacle and caused a severe flood by the sudden draining of a large part of the lake.2 A similar flood is recorded of the Sutlej in 1819. The shoulder of a mountain gave way in the deep gorge of the river, some twenty miles north-west of Simla, damming up the river to a height of 400 feet, and producing the usual devastating flood when the obstruction burst. The formation of a lake, 500 feet deep and 15 to 20 miles around, in the Shyok river of Baltistan, by the interposition of the snout of the Chong Kundun glacier across the valley, successively in the spring of the years 1924, 1927 and 1930 are recent instances. The bursting of the glacier barrier made the Indus at Attock, situated *00 miles downstream of the Shyok dam, rise in flood at each occasion. 1 Jammu and Kashmir Territories, London, 1875. * Bee. G.S.I. vol. xxvii. pt. 2, 1894.

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The increased volume of water, combined with the high velocity of the rivers in flood-time, multiplies their erosive and transporting power to an inconceivable extent, and boulders and blocks, several feet in diameter, are rolled along their bed, and carried in this manner to distances of fifty or even a hundred miles from their source, causing much injury to the banks and wear and tear to the beds of the channels.

of the Indus ; (3) the rivers belonging to the Ganges system which finally took a south-easterly course. ^ The elevation of Potwar into a plateau converted the north-west section of the main river into a separate independent drainage basin, with the Sutlej as its most easterly tributary. Hitherto the main river had travelled to its confluence with the Indus along a track which was a north-western prolongation of the present course of the Jumna, thence via the present bed of the Soan to the Indus. After these elevatory movements and separation of the north-west section, the remaining upper portion of the main channel was sub­ jected to a process of reversal of flow, its water being forced back by the Punjab elevations to seek an outlet into the Bay of Bengal along the now aggraded, more or less levelled sub-montane plains. In this reversal of the old drainage Pascoe assigns the chief share to process of river-capture by head-erosion of the tributaries. The competence of the agency of river-capture alone in accomplishing this farreaching change is debatable and differential earth-movement as the chief contributory cause is suggested, aided by the recently levelled and uniformly graded drainage-lines on the surface of these wide plains. The severed upper part of the Siwalik River became the modern Ganges, it having in course of time captured the transversely running Jumna and converted it into its own affluent. The transverse Him­ alayan rivers, e.g. the Alaknanda, Karnali, Gandak and Kosi, which are really among the oldest water-courses of North India, continued to discharge their waters into this new river, irrespective of its ulti­ mate destination, whether it was the Arabian Sea or the Bay of Bengal. During sub-Recent times some interchange took place be­ tween the easterly affluents of the Indus and the westerly tributaries of the Jumna by minor shiftings of the water-shed, now to one side now to the other. There are both physical and historical grounds for the belief that the Jumna during early historic times discharged into the Indus system, through the now neglected bed of the Saraswati river of Hindu traditions, its present course to Prayag being of late acquisition. The Punjab portion of the present Jhelum, Chenab, Ravi, Beas and utlej have originated after the uplift of the topmost stage of the iwalik system and subsequent to the severance of the Indus from e Ganges. The Potwar plateau-building movements could not but Ve rejuvenated the small rivulets of southern Punjab, which until °w were discharging into the lower Indus, the vigorous head-erosion

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Late Changes in the Drainage Systems of North India Many and great have been the changes in the chief drainage lines of North India since late Tertiary times 1—changes in fact which have produced a complete reversal of the directions of flow of the chief rivers of North India. v^The formation of the long thin belt of Siwalik deposits along the foot of the Himalayas from Assam, through Kumaon and the Punjab to Sind, widening steadily in its westward extension^ is now ascribed to the flood-plain deposits of a great north-west-flowing; river lying south of and parallel with the H im­ alayan chain from Assam to the furthest north-west corner of th e iFunj^b, and then flowing southwar3^to meet the gradually receding {Miocene sea of Sind and P u n ja b ^ This river has been named the ‘~SiwaIIk Kiver ” by Pilgrim and the “ Indobrahm ” by Pascoe, from the combined discharge of the Brahmaputra, Ganges and Indus which it carried at one time. This old river is believed t o be t he successor of the narrow strip of the sea—the remnant of th e Him­ alayan sea left after the main uplift of those mountains—as the latter gradually withdrew, through the encroachment of the delta of the replacing river, from Naini Tal, Solon, Muzaffarabad and Attock to Sind. The Nummulitic limestone deposits of these localities testify to the extent and boundary of the Eocene gulf. The final extinction of this gulf, which once stretched from Assam to Sind, left behind it a wide river-basin in which were laid down the thick series of Murree and Siwalik deposits during the interval between the Middle Miocene and the end of Pliocene. Post-Siwalik earth-movements in N.W. Punjab brought about a dismemberment of this river-system, which hitherto had flowed from the head-waters in Assam, through the whole breadth of India, to Potwar and thence to the receding head of the Sind Gulf, into three subsidiary systems : (1) The present Indus from north-west Hazara ; (2) the five Punjab tributary rivers 1 E. H. Pascoe, The Indobrahm, Quart. Journ. Geol. Soc., vol. lxxv. pp. 138-155 (1919); G. E. Pilgrim, The Siwalik River, Journ. Asiat. Soc. Beng., vol. xv. (New Series), pp. 81-99 (1919).

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resulting from this impetus enabled them to capture, one bit after the other, that portion of the Siwalik River which crossed the Potwar on its westerly course to the Indus. Ultimately the head-waters joining up with the youthful torrents descending from the mountains, these rivers grew much in volume and formed these five important rivers of the province, having their sources in the snows of the Great Himalaya Range and deriving their waters from as far east as the Manasarowar lake on the Kailas Range. The western portion of the broad but now deserted channel of the main river, after these mutil­ ating operations, has been occupied to-day by the puny, insignificant stream of the Soan, a river out of all harmony with its great basin and the enormous extent of the fluviatile deposits with which it is choked. The Himalayas are undergoing a very active phase of subaerial erosion, being a zone of recent folding and fracture, their disintegra­ tion is proceeding at a more rapid rate than is the case with older earth-features of greater geological stability. The plains of India and the Ganges delta are a fair measure of the amount of matter worn down from a section of the Himalayas since the Pliocene period. Landslips, soil-creep, breaking off of enormous blocks from the mountain-tops are phenomena familiar to visitors to these moun­ tains. The denudation in the dense forests of the hill-slopes in the Eastern Himalayas recalls that of the tropical lands in its intensity and character. REFERENCES H. B. Mcdlicott and W. T. Blanford, M anual of the Geology of India, vol. i., 1887, Introduction. Sir S. Burrard and Dr. A. M. Heron, The Geography and Geology of the Himalaya Mountains, Second Edition, 1932. Records of the Geological Survey of India, vol. xxxv. pts. 3 and 4 ; vol. xl. pt. 1 ; vol. xliv. pt. 4 ; vol. lxiii. pt. 2, 1930, Glaciers o f the Himalayas. Physical Atlas o f Asia, W. & A. K. Johnston. The Bathy-Orographical M ap o f India, W. & A. K. Johnston. W. H. Hobbs, Earth-Features and their Meaning, 1912 (Macmillan). Mt. Everest Expeditions : Publications by. 1921-33. Sven Hedin, Southern Tibet, vols. i-ix., Stockholm, 1917. Dainelli, Italian Expedition to the Himalaya and Karakoram (1913-14), vols. i.-xiii., Bologna, 1923-35. R. D. Oldham, The Evolution o f Indian Geography, Geographical Journal, London, March, 1894.

CHAPTER II STRATIGRAPHY OF INDIA—INTRODUCTORY

Correlation of Indian formations to those of the world—An outstanding difficulty in the study of the geology of India is the difficulty of correlating accurately the various Indian systems and series of rocks with the different divisions of the European stratigraphical scale which is accepted as the standard for the world. The difficulty be­ comes much greater when there is a total absence of any kind of fossil evidence, as in the enormous rock-systems of the Peninsula or in the outer zone of the Himalayas, in which case the determination of the geological horizon is left to the more or less arbitrary and unreliable tests of lithological composition, structure, and the degree of meta­ morphism acquired by the rocks. These tests are admittedly un­ satisfactory, but they are the only ones available for fixing the homology of the vast pre-Cambrian formations of the Peninsula, which form such an important feature of the pre-Palaeozoic geology of India. The basis of stratigraphy is the determination of the natural order of superposition of strata ; until the exact original succession of deposits in a stratified series is ascertained no correlation of strata at different localities is possible. I t is the function of stratigraphy to discover and arrange the sedimentary deposits of the earth’s crust in the order of their age, so th at each originally older bed is lower in position than the next newer one. Apart from the complications introduced by folding and faulting, which makes the application of the principle of superposition difficult, there is the difficulty arising from frequent lateral variations of sedimentary strata. A sandstone or limestone lying between two shale beds may thicken or thin out until the whole series become a group of sandstones or limestones or shales. The discovery of William Smith, at the end of the eighteenth century, that groups of strata are characterised by the preser­ vation in them of particular fossil organisms, and can be identified by them, laid the foundation of historical geology. In establishing 43

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correlations of formations in distant areas the following criteria are employed : (1) (2) (3) (4) (5) (6) (7)

The order of superposition. Fossil organisms. Lithological characters. Stratigraphical continuity. Unconformities. Degree of metamorphism. Tectonic and structural disturbance.

There is no question, of course, of establishing any absolute con­ temporaneity between the rock-systems of India and those of Europe, because neithei lithological correspondence nor even identity of fossils is proof of the synchronous origin of two rock-areas so far apart. Biological facts prove th at the evolution of life has not pro­ gressed uniformly or in a simple straightforward direction all over the globe in the past, but that in different geographical provinces the succession of life-forms has been marked by widely varying rates of evolution due to physical differences existing between them, and that the process of distribution of species from the centre of their origin is very slow and variable. The idea, therefore, of contemporaneity is not to be entertained in geological deposits of two distant areas, even when there is a perfect similarity in their fossil contents. What is essential is that the rock-records of India, discovered in the, various parts of the country, should be arranged in the order of their superposition, i.e. in a chronological sequence. They should be classified with the help of local breaks in their sequence, or by the evidence of their organic remains, and named according to some local terminology. The different outcrops should then be correlated among themselves. The last and the most important step is to correlate these, on the evidence of their contained fossils, or failing that, on lithological grounds, to some equivalent division or divisions of the standard scale of stratigraphy worked out from the fossiliferous rock-records of the world. In illustration of the above it may be remarked that the Carboni­ ferous system of Europe is characterised by the presence of certain types of fossils and by the absence of others. If in any part of India a series of strata are found, containing a suite of organisms in which many of the genera and a few of the species can be recognised as identical with the above, then the series of strata thus marked off is

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correlated with the Carboniferous system of Europe, though on account of local peculiarities and variations, the system is often desig­ nated by a local name. It is not of much significance whether they were or were not deposited simultaneously, so long as they point to the same epoch in the history of life upon the globe ; and since the history of the development of life upon the earth, in other words, the order of appearance of the successive life-forms, has been proved to be broadly uniform in all parts of the earth, there is some unity be­ tween these two rock-groups. As a substitute for geological syn­ chronism Prof. Huxley introduced the term Homotaxis, meaning “ Similarity of arrangement”, and implying a corresponding position in the geological series. The fauna and flora of the Jurassic system of Europe are considered homotaxial with those of some series of de­ posits in different parts of India, though it is quite probable th at in actual age any of these may have been contemporaneous with the end of the Triassic deposits in one part of the world or perhaps with the beginning of the Cretaceous in another. The different “ facies ” of Indian formations—I t often happens that one and the same geological formation in the different districts is composed of different types of deposits, e.g. in one district it is com­ posed wholly of massive limestones, and in another of clays and sand­ stones. These divergent types of deposits are spoken of as belonging to different facies, e.g. a calcareous facies, argillaceous facies, aren­ aceous facies, etc. There may also be different facies of fauna, just as much as facies of rock-deposits, and the facies is then distinguished after the chief element or character of its fauna, e.g. coralline facies, littoral facies, etc. Such is often the case with the rock-formations of India. From the vastness of its area and the prevalence of different physical conditions at the various centres of sedimentation, rocks of the same system or age are represented by two or more widely dif­ ferent facies, one coastal, another deep-water, a third terrestrial, and sometimes even a fourth, volcanic. The most conspicuous example of this is the Gondwana system of the Peninsula and its homotaxial equivalents. The former is an immense system of fresh-water and subaerially deposited rocks, ranging in age from Upper Carboniferous to Upper Jurassic, whose fossils are ferns and conifers, fishes and reptiles. Rocks of the same age, in the Himalayas, are marine lime­ stones and calcareous shales of great thickness, and containing deepsea organisms like Lamellibranchs, Cephalopods, Crinoids, etc., from the testimony of which they are grouped into Upper Carboniferous, •Permian, Triassic and Jurassic systems. In the Salt-Range these

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same systems often exhibit a coastal facies of deposits like clays and sandstones, with littoral organisms, alternating with limestones. In this connection it must be clearly recognised how these deposits, which are homotaxial, and more or less the time-equivalents of one another, should come to differ in their fossil contents. The reason is obvious. For not only are marine organisms widely different from land animals and plants, but the littoral species th at inhabit the sandy or muddy bottoms of the coasts are different from those pelagic and abysmal organisms th at find a congenial habitat in the clearer waters of the sea and at great distances from land. Again, the animal life of the seas of the past ages was not uniform, but it was distributed according to much the same laws as those th at govern the distribution of the marine biological provinces of to-day. The fossils entombed in some formations are of markedly local or provincial affinities. Provincialisation of faunas arises from various causes—the dependence of organisms on their environments, their isolation, or from relative preponderance or absence of competing species, or from physical barriers to migration of species. Pelagic, or free-swimming members of a fauna attain a wider horizontal or geographical distribution than bottom-living forms. I t thus arises th at the fossils present in a series of deposits are not a function of the period only when the deposits were laid down, but, as Lyell says, are a “ function of three variables ”, viz. (1) the geological period at which the rocks were formed, (2) the zoological or botanical provinces in which the locality was situated, and (3) the physical conditions prevalent at the time, e.g. depth, salinity and muddiness of water, temperature, character of the seabottom, etc. A new aid to stratigraphy that is slowly coming into vogue may be just mentioned. The epochal discovery th at minerals containing uranium and thorium break up into other elements through atomic disintegration, producing as a final residuum lead, the change taking place at a definite and measurable rate, has placed in the hands of the geologist a new weapon for the determination of the age of the great azoic pre-Cambrian systems. For India the investigation of leadratio and helium-ratio in some radio-active minerals occurring in the widely spread Archaean and Purana rock-systems may provide, when these methods are perfected, a guide to their correlation in distant areas, as well as a measure of their absolute ages, facts which are at present but vaguely knowable. The chief geological provinces of India—The following are the im­ portant localities in the country, besides some areas of the Peninsula,.

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wherein the marine fossiliferous facies of the Indian formations are more or less typically developed : 1. The Salt-Range.

[This range of mountains is a widely explored region of India. It was one of the earliest parts of India to attract the notice of the geologists, both on account of its easily accessible position as well as for the conspicuous manner in which most of the geological systems are displayed in its pre­ cipices and defiles. Over and above its stratigraphic and palaeontological results, the Salt-Range illustrates a number of phenomena of dynamical and tectonic geology.]' 2. The Himalayas.

[As mentioned in the first chapter, a broad zone of sedimentary strata lies to the north of the Himalayas, behind its central axis, occupying a large part of Tibet. This is known as the Tibetan zone of the Himalayas. This zone of marine sediments contains one of the most perfect develop­ ments of the geological record seen in the world, comprising in it all the periods of earth-history from the Cambrian to the Eocene. It is almost certain that this belt of sediments extends the whole length of the Him­ alayan chain, from Hazara and Kashmir to the furthest eastern extremity ; but so far only two portions of it have been surveyed in some detail, the one the north-west portion—the Kashmir Himalayas—and the other the mountains of the central Himalayas north-east of the Simla region, especially the Spiti valley, and the northern parts of Kumaon and Garhwal.] (i) North-West Himalayas.

[This area includes Hazara, Kashmir, the Pir Panjal, and the ranges of the outer Himalayas. A very complete sequence of marine Palaeozoic and Mesozoic rocks is met with in the inner zone of the mountains, while a complete sequence of Tertiary development is seen in the outer, Jammu hills. The Kashmir basin, lying between the Zanskar and the Panjal ranges, contains the most fully developed Palaeozoic system seen in any part of India. For this reason, and because of the easily accessible nature of the formations to parties of students, in a country which climatically forms one of the best parts of India, the geology of Kashmir is treated in a separate chapter at the end of the book.] (*i) Central Himalaya*.

[Many eminent explorers have unravelled the geology of these moun­ tains since the early ’thirties of the last century, and parts of this region, hke Spiti, form the classic ground of Indian geology. The central Himalayas include the Simla hills, Spiti, Kumaon and Garh^al provinces. The great plateau of Tibet ends in the northern parts of hese areas in a series of gigantic south-facing escarpments, wherein the stratigraphy of the northern or Tibetan zone of the Himalayas, referred to * °ye, is typically displayed. The Spiti basin is the best known for its °ssil wealth as well as for the completeness of the stratigraphic succession

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from the Cambrian to Cretaccous. The systems of Kashmir are on a north­ west continuation of the strike of the Spiti basin. Much detailed work has been done of late years in the Simla-Chakrata area.] 3. Sind.

[Sind possesses a highly fossiliferous marine Cretaceous and Tertiary record. The hills of the Sind-Baluchistan frontier contain the bestdeveloped Tertiary sequence, which is recognised as a type for the rest of India.] 4. Rajputana.

[Besides the development of a very full sedimentary record, divided into three pre-Palaeozoic systems of Archaean-Dharwar age and an interesting facies of the Vindhyan system in the Aravalli range, Western Rajputana contains a few isolated outcrops of marine Mesozoic and early Tertiary strata underneath the Pleistocene desert sand, which has concealed by far the greater part of its solid geology.] 5. Burma and Baluchistan.

[These two countries, at either extremity of the extra-Peninsular area, contain a large section of the stratified marine geological record which helps to fill up the gaps in the Indian sequence. Many of these formations are again highly fossiliferous, and afford good ground for comparison with their Indian congeners. Within the geographical term “ India ” is now in­ cluded all these regions which are regarded as its natural physical extension on its two borders—Afghanistan and Baluchistan on the west and Burma on the east. The student of Indian geology is therefore expected to know of the principal rock-formations of Baluchistan and Burma.] 6. Coastal System of India.

[Along the eastern coast of the Peninsula and to a less extent on the Mekran coast, there is a strip of marine sediments of Mesozoic, Tertiary or Quaternary ages, in more or less connected patches—the records of several successive “ marine transgressions ” on the coasts.] Peninsular India, as must be clear from what we have seen regard­ ing its physical history in the first chapter, is a part of India which contains a most imperfectly developed geological record. The Palaeozoic group is unrepresented but for the fluviatile Permian for­ mations ; the Mesozoic era has a fairly full record, but except as regards the Cretaceous it is preponderatingly made up of fluviatile, terrestrial and volcanic accumulations ; while the Tertiary is almost unrepresented except by the partly Eocene lavas forming the Deccan Traps. The student of Indian geology should first familiarise himself with the representatives of the various geological systems that are found in these provinces of India correlated to the principal divisions of the European sequence.

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49

The idea of a geological system is not confined to a summary of facts regarding its rocks and fossils. These are the dry bones of the science ; they must be clothed with flesh and blood, by comparing the processes and actions which prevailed when they were formed with those which are taking place before our eyes in the world of to-day. A sand-grain or a pebble of the rocks is not a mere particle of inani­ mate matter, but is a word or a phrase in the history of the earth, and has much to tell of a long chain of natural operations which were con­ cerned in its formation. Similarly, a fossil shell is not a mere chance relic of an animal that oncc lived, but a valuable document whose pre­ servation is to be reckoned an important event in the history of the earth. That mollusc to which the shell belonged was the heir to a long line of ancestors and itself wTas the progenitor of a long line of descen­ dants. Its fossil shell marks a definite stage in the evolution of life on earth that was reached at the time of its existence, which definite period of time it has helped to register. Often it tells much more than this, of the geography and climate of the epoch, of its contemporaries and its rival species. In this way, by a judicious use of the imagina­ tion, is the bare skeleton given a form and clothed ; the geological records then ceasc to be an unintelligent mass of facts, a burden to memory, and become a living story of the various stages of the earth’s evolution. In reading stratigraphical geology the student should remind him­ self to take note of the illustrations of the principles of dynamical and tectonic geology, of which every page of historical geology is full. Many of the facts of dynamical and structural geology find a pertinent illustration by the part they play in the structure or history of a par­ ticular country or district. The problems of crust-deformations, of vulcanicity, of the variations, migrations and extinctions of life-forms with the passage of time, and a host of other minor questions that are inscribed in the pages of the rock-register, must be thought over and interpreted with the clue th at modern agencies in the earth’s dynamics furnish. REFERENCES

Sir T. H. Holland, Im perial Gazetteer of India, vol. i. chapter ii.,

1907. ‘irr, Principles of Stratigraphic Geology (C.U. Press). ° r^ P P er> Mem. G .S.I. vol. xliii. pt. 1, Indian Geological Terminology, A W n an .

( Raniganj | Ironstone 1 shales. 1 Barakar.

„ •'BU'BA\pUOj[) - d j^

Panchet.

Durgapur.

Rajmahal. -• S

m a rin e beds.

Motur Barakar. Umaria,

Bijori.

Barakar.

Panchet o r Mangli. Tiki.

s a n d s to n e .

Parsora.

^

Panchet.

Pachmarhi.

s a n d s to n e )

Bagra Denwa. Chicharia. Dubrajpur

Jabalpur. Rajmahal.

Maleri.

Kota (Athgarh

Chikiala. Jabalpur. Chaugan. -

Satpu ra . MaV al. and

S on

hanadi

1

a jm a h a l .

R D am odar Val.

* rs tj JS J-1 -s '5*

« 'i 1

-a , ~ •BUUAVpUOQ -J'-J

The relationship of the Kota and Rajmahal stages is uncertain and it is possible that the Kota beds are younger than the Rajmahal beds.

PermoCarboniferous.

Upper Permian. Middle Permian.

Bunter.

Keuper a n d Rhaetic. Muschelkalk.

Lias.

Upper J urassic. Jabal­ pur.

Lower Cretaceous. Umia.

Tripety, Pavalur, e t c . Raghavapuram, Sripermatur,

G odavari Val.

j

E

ast

Co a st.

Cutch.

Age.

GEOLOGY OF IN D IA

System . S e r ie s . Sta ges.

II. Table of Correlation of tlie Series and Stages of the Gondwana System in different parts of Peninsular Lndia.

130

131

dropped in the Talchir basins, in which the deposition of fine silt was going on. Proofs of similar glacial conditions at this stage exist in many other parts of India, viz. the Aravallis, Rajputana, Salt-Range, Hazara and Simla. The Aravallis, it appears, were the chief gathering-grounds for the snow-fields at this time, from which the glaciers radiated out in all directions. Many parts of the Southern Hemisphere, as shown on Table on page 130, experienced glacial conditions at this period. Boulder-conglomerates (tillites) homotaxial with the Talchir stage occur in South Africa (Dwyka series), South-East Australia (Murree Series) and in South America (Itarara boulder-beds). Talchir fossils—Fossils are few in the Talchir stage, the lower beds being quite unfossiliferous, while only a few remains of terrestrial organisms are contained in the upper sandstones ; there are impres­ sions of the fronds of the most typical of the Lower Gondwana seed ferns Gangamopteris and Glossopteris with its characteristic stem, named Vertebraria ; also spores of various shapes have been found on some fertile fronds; wings of insects, worm-tracks, etc., are the only signs of animal life. The Talchir stage is succeeded by a group of coalbearing strata known as the Karharbari stage, 500-600 feet in thick­ ness, also of wide geographical prevalence. The rocks are grits, conglomerates, felspathic sandstones and a few shales, containing seams of coal. Plant fossils are numerous, the majority of them be­ longing to genera of unknown affinity, provisionally referred to the class of seed-ferns (Pteridosperms). The chief genera are : (Pteridosperms) Gangamopteris—several species—this genus being represented a t its best in the Karharbari stage ; Glossopteris and its stem Vertebraria, Gondwanidium (formerly known as Neuropteridium); (Cordaitales) Noeggerathiopsis, Euryphyllum. (Equisetales) Schizoneura. (Incertae) Buriadia, OttoJcaria, Arberia. Besides there occur the seed-like bodies Samaropsis and Cordaicarpus, as well as scales with an entire or lacerated margin. Damuda series—The Talchir series is succeeded by the second divi­ sion of the Lower Gondwanas, the Damuda series, the most important portion of the Gondwana system. Where fully developed, as in the Damuda area of Bengal, the series is divided into three stages, in the descending order: Raniganj—5000 feet. Ironstone shale—1400 feet. Barakar — 2 0 0 0 feet.

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GEOLOGY OF IN D IA

Of these the Barakar stage, named from the Barakar branch of the Damodar river, alone is of wide distribution among the Gondwana basins outside Bengal, viz. in the Satpura and the Mahanadi and Godavari valleys ; the middle and upper members are missing from most of them, being restricted chiefly to the type-area of the Damodar valley. The Barakar stage rests conformably upon the Talchir series, and consists of coarse, soft, usually white, massive sandstones and shales with coal-seams. The Barakars contain a large quantity of coal in *thick coal-seams, though the quality of the coal is variable. The per­ centage of the carbon is sometimes so low that the coal passes into mere carbonaceous shale by the large admixture of clay. I t is usually composed of alternating bright and dull layers. 1 The coal is often spheroidal, i.e. it breaks up into ball-like masses. The Ironstone shales are a great thickness of carbonaceous shales with concretions (Sphaerosiderites) of impure iron-carbonate and oxides. They have yielded much ore of iron. But this group is of a most inconstant thickness and appears only at a few localities in the Damuda area, being altogether missing from the rest of the Gondwana areas. This l is succeeded by the Raniganj stage of the Damuda series, named from | the important mining town of Bengal. The Raniganj stage is com­ posed of massive, false-bedded, coarse and fine sandstones and red, brown and black shales, with numerous interbedded coal-seams. The sandstones are felspathic, but the felspar in it is all decomposed, i.e. kaolinised. The coal is abundant and of good quality as a fuel with a percentage of fixed carbon generally above 55. Igneous rocks of Damuda coal-measures—Many of the coalfields of the Damodar valley, especially those of the eastern part, are in­ vaded by dykes and sills of an ultra-basic rock which has wrought much destruction in the coal-seams by the contact-metamorphism it has induced. The invading rock is a mica-peridotite, containing a large quantity of apatite. The peridotite has intruded in the form of dykes and then spread itself out in wide horizontal sheets or sills. Another intrusive rock is a dolerite, whose dykes are thicker, but they are fewer and are attended with less widespread destruction of coal than the former. j Effects of contact-metamorphism—The coal is converted into coke, and its economic utility destroyed. The reciprocal effects of contactmetamorphism on the peridotite as well as the coal are very instruc­ tive to observe. The peridotite has turned into a pale earthy and friable mass with bronze-coloured scales of mica in it, but without any

I

1C. S. Fox, Natural History of Indian Coal, Mem. O.S.I. lvii, 1931.

L O W E R G O ND W A NA SYSTEM

133

other trace of its former crystalline structure. On the other hand, the coal has coked or even burnt out, becoming light and cindery, and at places it has developed prismatic structure. The Damuda flora—The Damuda fossils are nearly all plants. The flora is chiefly cryptogamic, associated with only a few spermaphytes. It is exceedingly rich in Pteridosperm leaves of the net-veined type, the genus Glossopteris here attaining its maximum develop­ ment, while Gangamopteris is on the decline. The following are the most important genera : (Pteridosperms)—Glossopteris with Vertebraria, at least nine species, several of them confined to the Raniganj stage, Gangamopteris, Belemnopteris, Merianopteris, Sphenopteris, Pecopteris, Palaeovittaria. (? Ginkgoales)—Rhipidopsis. (Cordaitales)—Noeggerathiopsis, Dadoxylon. (Cycadophyta)—Taeniopteris, Pseudoctenis. (Filicales)—Cladophlebis. (Equisetales)—Schizoneura, Phyllotheca. (Sphenophyllales)—Sphenophyllum. (Lycopodiales)—? Bothrodendron. (Incertae)—Barakaria, Dictyopteridium, scales, seeds including Samaropsis and Cordaicarpus. The animals include,Estheria, Labyrinthodonts and some Fishes. The Damuda series of other areas—In the Satpura area the Da­ muda series is represented, in its Barakar and Raniganj stages, by about 1 0 , 0 0 0 feet of sandstone and shale, constituting what are known as the Barakar, Motur and Bijori stages respectively of this province. The Mohpani and the Pench valley coalfields of the Satpura region belong to the Barakar stage of this series. In the strata of the last-named stage, at Bijori, there occur bones and other remains of a Labyrinthodont (Gondwanosaurus). Other fossils include scales and teeth of ganoid fishes, and seed-ferns and equisetums identical with those of Bihar. It is quite probable that large expanses of the Lower Gondwana rocks are buried under the basalts of the Satpuras, which must have contained, and possibly still contain, some valuable coal-seams. Another area of the Peninsula where the Damuda series is recog­ nised, though greatly reduced and with a somewhat altered facies, is in the Godavari valley, where a long but narrow band of Lower Gondwana rocks stretches from the old coalfield of Warora to the

134

GEOLOGY OF IN D IA

neighbourhood of Rajahmundri. The Barakar stage of the Damuda series prevails in these outcrops which bear the coal-fields of Warora, Singareni, Bellarpur, etc. One more outcrop of the Damuda group is seen in the Rewah State, Central India, which at one or two places contains workable coalseams, e.g. in the Umaria field. The division of the Lower Gondwana exposed in this field also is the Barakar. Homotaxis of the Damuda and Talchir series—Few problems in the geology of India have aroused greater controversy than the problem of the lower age limit of the Gondwana system. The Talchir series has been referred, by different authors, to almost every stratigraphic position from Lower Carboniferous to Trias. The discovery, however, of a Lower Gondwana horizon in Kashmir, bearing the eminently characteristic^genera Gangamopteris and Glossopteris overlying the Upper Carboniferous and underlying marine fossiliferous strata of undoubtedly Permian age, has settled the question beyond doubt. A similar occurrence of Lower Gondwana plants has Feen noted in the Lower and Middle Productus limestone of the Salt-Range, the marine fossils of which point to Lower and Middle Permian affinities. The JJpper Carboniferous, or Permo-Carboniferous age, attributed to the Talchir glacial lioHzon SyTEis circumstance is quite in keeping with the internal evid'enceTHIt is Furnished by the Talchir and Damuda floras, as well as b y tTTelTsTi and labyrinthodont. remains ofBijbri. The eminent American palaeontologist, Professor CharIes~ScluciBier^ has, however, ascribed a definitely Permian (Lower to Middle) age to the Talchir glacial epoch. ^Further positive evidence leading to the same_inference is supplied Jyy the Lower Gondwanas of Victoria and New South Wales, Australia. Here, Gangamopteris and other plant-bearing beds of undoubted Crondwana facies, underlain by a glacial deposit, identical with the Talchir boulder-bed, are found interstratified with marine beds which contain an Upper Carboniferous fauna with Eurydesmn,^ rftsp.mblinp; that of the Speckled sandstone group of the Salt-Range. ^ Economics—The Damuda series contains a great store of mineral wealth in its coal-measures, and forms, economically, one of the most productive horizons in the geology of India. I t contains the most valuable and best worked coal-fields of the country. The mining operations required for the extraction of coal from these rocks are comparatively simple and easy because of the immunity of the Gondwana rocks from all folding or plication. Also, mining in India is not so dangerous on account of the less common association of

L O W ER GO ND W A NA SYSTEM

135

highly explosive gases (marsh-gas or “ firedamp ”) with the coal as com p ared with European coal fields. There are, however, special difficulties associated with the working of thick seams, and fires and subsidences have proved very troublesome. [Although coal occurs in India in some later geological formations also— e q. in the Eocene of Assam, the Punjab, Rajputana and Baluchistan, and in the Jurassic rocks in Cutch—the Damuda series is the principal source of Indian coal, contributing nearly 98 per cent, of the total coal production. The principal fields are those of Bihar—Raniganj, Jharia, Giridih and Bokaro. The Raniganj coalfield covers an area of 500 square miles, con­ taining many seams of good coal with interbedded ironstones. The thickness of the individual seams of coal is great, often reaching to forty or fifty feet, while a thickness of eighty or more feet is not rare. The annual output of coal from the Raniganj mines is more than six million tons. The Jharia field has at present the largest output, 10,000,000 tons per annum. The coal of the Jharia fields belongs in geological age to the Barakar stage. It has less moisture and greater proportion of fixed carbon than that of the Raniganj stage. The coal-fields of Bokaro, to the west of Jharia, contain thick seams of valuable coal. Their total resources are estimated at 1500 million tons. Besides the foregoing there are smaller fields in the Damodar valley. The coal-fields of the other Gondwana areas are not so productive, the more important of them being the Umaria field of Central India in Rewah, the Pench valley and Korea and Bellarpur fields of the Central Provinces, and the Singareni of Hyderabad. But the aggregate yield of these extra-Bihar fields is a little over two million tons per annum.] Besides coal, iron is t^e chief product minefl from the Damuda rocks, while beds of fire-clay, china-clay or kaolin, terra-cotta clays for the manufacture of fire-bricks, earthenware and porcelain, etc., occur in considerable quantities in Bihar and the Central Provinces. The Barakar sandstones and grits furnish excellent material for mill­ stones. Classification—During recent years Dr. G. de P. Cotter, in an a t­ tempt to subdivide the Gondwana system on palaeobotanical basis, has found it more appropriate, on the evidence of an interesting suite of plant fossils obtained from the Parsora beds of South Rewa, to include among the Lower Gondwanas the thick zone of strata which overlies the Damuda series and underlies the Rajmahal, em­ bodying in fact the group that has been here treated as Middle Gon­ dwana. Dr. Cotter names these strata in question Panchet series (divided into three stages—Panchet, Maleri amd Parsora) and groups them along with the Talchir and Damuda series in the Lower Gon­ dwana. Dr. C. S. Fox in his comprehensive Memoir on the Gondwana system has adopted a different grouping of this middle series. In

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GEOLOGY OF IN D IA

his scheme of classification the Maleri and Parsora scries are included in the Upper Gondwanas while the Panchets are grouped with the Lower. The flora of the beds placed in the Parsora stage by Cotter still needs a critical examination. Possibly the fossils belong to two dis­ tinct horizons, the older (containing a typical Glossojpteris flora) de­ finitely belonging to the Lower Gondwanas, the younger (with Thinnfeldia as the dominant genus) belonging to the Middle or Upper Gondwanas. According to Seward and Sahni the affinities of the latter flora are also distinctly with the Lower rather than with the Upper Gondwana (see page 141). Sahni holds the view th at on the palaeobotanical evidence the Parsora beds cannot possibly be classed as Jurassic. The classification that is here adopted was originally based on the views of Feistmantel and Vredenburg, but chiefly on lithological considerations and the physical conditions of the period embracing the Middle Gondwanas, which were strikingly different from those prevailing in the Damuda and Rajmahal eras.

4

CHAPTER X THE GONDWANA SYSTEM (continued)

2. MEDDLE GONDWANAS B e t w e e n the upper beds of the Damuda series and the next overlying group of strata, distinguished as the Panchet, Mahadev, Maleri and Parsora series, there is an unconformable junction ; in addition there exists a marked discordance in the lithological composition and in the fossil contents of these groups. For these reasons the series overlying

The presence of red beds, indicating arid or semi-desert conditions super­ vening on the damp forest climate of the Damuda period, the Triassic affinities of the fossil reptiles and stegocephalian amphibia and the coincidence of the Palaeo-Mesozoic boundary at the base of the Panchets with the uncon­ formity at the top of the Raniganj series are features distinguishing the Middle Gondwana group. The total extinction of Gangamopteris and the Sphenophyllales after the Damuda epoch is widespread and denotes a datum-line of some importance. The Middle Gondwana was also the epoch of most extensive land-conditions in India. During the Upper Gondwana epeiric seas began to encroach on its borders from the north* west and south-east.

1. Archaean. 2. Talchir. 3. Damuda.

4. Pachmarhi (Kamthi). 5. Denwa (Maleri) and Bagra.

6. Jabalpur. 7. Deccan Trap.

Medlicott, Mem. O.S.I. vol. x (1873).

the coal-bearing Damudas have been separately grouped together under the name of Middle Gondwanas by Mr. E. W. Vredenburg. 1 Usually it is the practice to regard a portion of the latter group as 1 Summary of the Geology of India, Calcutta, 1910. 137

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GEOLOGY OF IN D IA

forming the upper portion of the Lower Gondwanas, and the remain ing part as belonging to the bottom part of the Upper Gondwanas, but, in view of the above dissimilarities, as well as of the very pronounced lithological resemblance of what are so distinguished as the Middle Gondwanas with the Triassic system of Europe, it is convenient, for the purpose of the student at any rate, to regard the middle division as a separate section of the Gondwana system. Rocks—The rocks which constitute the Middle Gondwanas are a great thickness of massive red and yellow coarse sandstones, con­ glomerates, grits and shales, altogether devoid of coal-seams or of carbonaceous m atter in any shape. Vegetation, which flourished in such profusion in the Lower Gondwanas, became scanty, or entirely disappeared, for the basins in which coarse red sandstone were de­ posited must ha ve furnished very inhospitable environments for any luxuriant growth of plant life. The type area for the development of this formation is not Bihar but the Mahadev hills in the Satpura Range, where they form a continuous line of immense escarpments which are wholly composed of unfossiliferous red sandstone. (See Fig. 15, sketch map of the Mid-Gondwanas of the Satpura area, and Fig. 16, generalised section across it.) On this account the Middle Gondwanas have also received the name of the Maliadev series. The railway from Bombay to Jabalpur, just east of Asirgarh, gives a fine view of these massive steep scarps looking northwards. The other localities where the strata are well developed, though not in equal proportions, are the Damuda valley of Bengal and the chain of basins of the Godavari area. The whole group of the Middle Gondwanas is sub-divided into three series, of which the middle alone is of wide extension, the other two being confined to one or two local develop­ ments : Maleri (and Parsora) series—variable thickness. Mahadev (or Pachmarhi) series—3000 feet to 8000 feet. Panchet series—1500 feet. Panchet series—The Panchet series rests with a slight unconformity on the denuded surface of the Raniganj stage and at some places on jthe Barakars through overlapping of the former. The beds consist of (alternations of fine red clays and coarse, micaceous and felspathic sand­ stones, occasionally containing rolled fragments of Damuda rocks. The felspar in the sandstones is in undecomposed grains. Character­ istic Panchet plant fossils are : Schizoneura gondwanensis, Glossop­ teris, Vertebraria indica, Pecopteris concinna, Cyclopteris, Thinn-

M ID D L E GO NDW ANAS

feldia. The group is of importance, as containing many well-preserved remains of vertebrate animals, affording us a glimpse of the higher land-life that inhabited the Gondwana continent. These vertebrate fossils consist of the teeth, scales, scutes, jaws, vertebrae and other bones of ter­ restrial and fresh-water fishes, amphibians and reptiles. Three or four genera of labyrinthodonts (belonging to the extinct order Stegocephala of the amphibians) have been discovered, besides several genera of primitive and less differentiated reptiles. Panchet fossils : (Amphibia) Gonioglyptus, Glyptognathus, and Pachygonia; (Fish) Amblypterus ; (Reptiles) Dicynodon and Ptychosiagum and the dinosaur Epicampodon. The fresh-water crustacean Estheria is very abun­ dant a t places. Mahadev series—The Mahadev series, locally also named Pachmarhi, is the most conspicuous and the best-developed member of the Middle Gondwana in the Central Pro­ vinces. Near Nagpur it consists of some i 4000 feet of variously coloured massive | sandstones, with ferruginous and micaceous I clays, grits and conglomerates. The most typical development of the series is, however, in the Mahadeva and Pachmarhi hills of the Satpura range, where it is exposed in the gigantic escarp­ ments of these hills. It unconformably overlies the Bijori stage there (Raniganj stage of Damodar valley area). Here the series is composed essentially of thickbedded massive sandstones, locally called Pachmarhi sandstones, variously coloured

139

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GEOLOGY OF IN D IA

by ferruginous m atter ; in addition to sandstone there are a few shale beds which also contain a great deal of ferruginous matter, with sometimes such a concentration of the iron oxides in them locally that the deposits are fit to be worked as ores of the metal. The sandstones as well as shales are frequently micaceous. The shales contain beau­ tifully preserved leaves of seed-ferns and equisetaceous plants along their planes of lamination. Some animal remains are also obtained, including parts of the skeletons of vertebrates similar to those occur­ ring in the Panchet beds. The most important is an amphibian— Brachyops. This labyrinthodont was obtained from a quarry of fine red sandstone which lies at the bottom of the series forming a group known as the Mangli beds near the village of Mangli. The flora of the Pachmarhi series consists of seed-ferns and equisetums, several species of Vertebraria and Phyllotheca being found with the ferns Glossopteris, Gangamopteris, with Pecopteris, Angiopteridium, and Thinnfeldia; the species T. hughesi being very characteristic of the Pachmarhi. This flora resembles th at of the Damuda series in many of its forms, being for the most part the survivors of the latter flora. V Maleri series—The Maleri (or Denwa) series comes generally con­ formably on the top of the last. Its development is restricted to the Satpura and Godavari regions. Lithologically it is composed of a thick series of clays with a few beds of sandstones. Animal remains are abundant. The shales are full of coprolitic remains of reptiles. Teeth of the Dipnoid fish Ceratodus, similar to the mud-fish living in the fresh waters of the present day, and bones of labyrinthodonts like Mastodonsaurus, Gondwanosaurus, Capitosaurus and Metopias are met with in the Maleri rocks of Satpura, recognised there under the name of Denwa beds. Three reptiles, identical in their zoological re­ lations with those of the Trias of Europe, are also found in the rocks ; they are referred to the genera Hyperodapedon (order Rhynchocephala), Belodon, and Parasuchus (order Crocodilia). The Maleri group is well represented in the Godavari valley in the Hyderabad State also, and it is from the discovery of reptilian remains at Maleri, a village near Sironcha, that the group has taken its name. I t here rests with an unconformity on the underlying Mangli, or Panchet beds, and consists of bright red clays with pale-coloured sandstone beds. The shales are full of coprolite remains of reptiles together with their teeth, vertebrae and limb-bones, the above three fossil genera having been met with here also. Other fossils from the same locality include Ceratodus and the reptiles of the genus Hyperodapedon and Parasuchus. While the animal fossils clearly indicate a Triassic age, some plant-remains re­

M ID D L E GO NDW ANAS

141

corded by Feistmantel1 from Naogaon west of Maleri are character­ istic Upper Gondwana fossils common in the Kota and Jabalpur stages, and would point definitely to a J urassic horizon. These species j^j.0 Araucantes cutchensis and Elatocladus jabalpurensis.^ The Maleri group is succeeded by the Kota stage. Its affinities, however, are with the Upper Gondwanas, and will be described in connection with them. The combined groups were sometimes de­ signated as the Kota-Maleri stage. Reptilian fossils have also been collected from the Tiki beds of South Rewah, representing approxi­ mately the Maleri horizon of other Gondwana centres. The Tiki sandstones and shales have yielded some fragmentary bones among which are maxillae and vertebrae of Hyperodapedon, teeth and other relics of Dinosaurs, together with shells of the fresh-water lamellibranch Unio. The Parsora stage : This name is given by Dr. Cotter to a group of beds in South Rewah, stratigraphically denoting a horizon corres­ ponding roughly with the Rhaetic stage of Trias. These beds con­ stitute the typical Middle Gondwanas of Feistmantel. The Parsoras have yielded a flora of somewhat uncertain affinities containing ele­ ments of both Lower and Upper Gondwana type which still await a critical examination. Among the fossils collected from the villages of Parsora and Chicharia the dominant genus is Thinnfeldia (Dicroidium). This is represented by T. (D.) hughesi and several species allied to those known from other parts of Gondwanaland, where the intro­ duction of the Thinnfeldia element marks the later (Permo-Triassic) phases of the Glossopteris flora. From localities further south a flora apparently somewhat older, with Glossopteris as the chief genus, has been collected. I t is possible that the latter is a typical Lower Gond­ wana flora, distinct from the northern set characterised by Thinn­ feldia. In th at case only the beds round Parsora should be included in the Middle Gondwanas. Triassic age of the Middle Gondwanas—From the foregoing account of the Middle Gondwanas it must have been clear th at they agree in their lithology with the continental facies of the Triassic (the New Red Sandstone) system of Europe. At the same time the terrestrial forms of life, like the crustaceans, fish, amphibia and rep­ tiles that are preserved in them, indicate that they are as akin bio­ logically as they are physically to the English Trias. There are, how1See Feistmantel, Pal. lndica, Fossil Flora of the Gondwana System. (1877), vol. ii., Pt- 2, p. 16 ; (1879) vol. i., pt. 4, pp. 198-208. *Sahni, Pal. lndica, vol. xi (1931), pp. 115-116.

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GEOLOGY OF IN D IA

over, no indications in these rocks of that wonderful differentiation of reptilian life which began in the Triassic epoch in Europe and America, and gave rise, in the succeeding Jurassic period, to the numerous highly specialised races of reptiles that adapted themselves to life in the sea and in the air as much as on the land, and performed in that geological age much the same office in the economy of nature as is now performed by the class of Mammals. 3. THE UPPER GONDWANA SYSTEM Distribution—Upper Gondwana rocks are developed in a number of distant places in the Peninsula, from the Rajmahal hills in Bengal to the neighbourhood of Madras. The outcrops of the Upper Gondwanas, as developed in their several areas, viz. Rajmahal hills, Damuda valley, the Satpura hills, the Mahanadi and Godavari valleys, Cutch and along the Eastern coast, are designated by different names, because of the difficulty of precisely correlating these isolated outcrops with each other. I t is probable that future work will reveal their mutual relations with one another more clearly, and will render pos­ sible their grouping under one common name. In Cutch and along the Coromandel coast, beds belonging to the upper horizon of the Gondwanas are found interstratified with marine fossiliferous sedi­ ments, a circumstance of great help to geologists in fixing the time­ limit of the Upper Gondwanas, and determining the homotaxis of the system in the stratigraphical scale. Lithology—Lithologically the Upper Gondwana group is com­ posed of the usual massive sandstones and shales closely resembling those of the Middle Gondwanas, but is distinguished from the latter by the presence of some coal-seams and layers of lignitised vegetable matter, and a considerable development of limestones in some of its outcrops ; while one outcrop of the Upper Gondwanas, viz. that at the llajmahal hills, is quite distinct from the rest by reason of its being constituted principally of volcanic rocks. This volcanic formation is composed of horizontally bedded basalts contemporaneously erupted, which attain a great thickness. Rajmahal series—Upper Gondwana rocks are found in Bengal and Bihar at two localities, the Damodar valley and the Rajmahal hills, some 30 miles N.E. of the Raniganj coal-field, the latter being the more typical locality. The Upper Gondwanas in the Rajmahal hills rest unconformably on the underlying Barakar stage. The lowest beds above the break are known under the name of the Dubrajpur sand­

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stone ; the Rajmahal series consists of 2000 feet of bedded basalts or dolerites, with about 1 0 0 feet of interstratified sedimentary beds (intertrappean beds) of siliceous and carbonaceous clays and sandstones. Almost the whole mass of the Rajmahal hills is made up of the vol­ ca n ic flows, together with these inter-trappean sedimentary beds. The shales have turned porcellanoid and lydite-like on account of the co n ta c t-effe cts of th e basalts. The basalt is a dark-coloured, porphyritic and amygdaloidal rock, commonly fine-grained in texture. When somewhat more coarsely crystalline it resembles a dolerite. The amygdales are filled with beautiful chalcedonic varieties of silica, calcite, zeolites or other secondary minerals. A radiating columnar structure due to “ prismatic ” jointing is produced in the fine-grained traps at many places. I t is probable that these superficial basaltflows of the Rajmahal series are connected internally with the dykes and sills that have so copiously permeated the Raniganj and other coal-fields of the Damuda region, as their underground roots. The latter are hence the hypabyssal representatives of the subaerial Rajmahal eruptions. Among these dykes mica-peridotites, lamprophyre, minette and kersantite types have been found. The andesitic trap of Sylhet, in the Khasi hills of Assam, uncon­ formably underlying the Upper Cretaceous, is probably an eastward continuation of the Rajmahal trap. Rajmahal flora—-The silicified shales of the Rajmahal beds have yielded a very rich flora in which the fossil Cycads (Bennettitales) are the predominant group. Next in order of abundance are the Ferns and Conifers. The cycad genera comprise many types of leaves (e.g. Ptilophyllum, Pterophyllum, Dictyozamites, Otozamites, Nilssonia, Taeniopteris), also a few flowers (Williamsonia) and stems (Bucklandia). The stem known as Bucklandia indica bore leaves of the Ptilophyllum type and Williamsonia flowers ; the connections of the other leaf genera are still unknown. The most important Fern genera are Marattiopsis, Cladophlebis, Coniopteris, Gleichenites and Sphenopteris. The Coniferales include several kinds of vegetative shoots (Elatocladus, Brachyphyllum, Retinosporites), detached cones and scales (Conites, Ontheodendron, Araucarites) and wood (Araucarioxylon). The Equisetales are represented by Equisetites and the Lycopodiales by Lycopodites. Among the Incertae are some geriera (Rajmahalia, Homoxylon, Pentoxylon, etc.) of much palaeobotanical interest. Homoxylon rajmahalense is a type of fossil wood which closely resembles the wood of some Jurassic Cycads as well as th at of some primitive modern angiosperms. I t therefore supports the

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well-known theory of tlie Bennettitalean origin of angiosperms. The Rajmahal flora was till recently known almost exclusively from impressions. Recent anatomical studies by Professor Sahni and his pupils have considerably advanced our knowledge of this classical flora. The Rajmahal stage can fitly be called an age of fossil cycads, from the predominance of the Bennettitales. The flora presents a sharp contrast with those of the Lower and Middle Gondwanas. It wears a distinctly more familiar aspect, the affinities of the great majority of the genera being known. The Pteridosperms and the Cordaitales have disappeared. The Equisetales have dwindled into insignificance. The Ferns now claim an important place, and most of them can be assigned to recent families. The conifers, formerly a small group, are now on the increase ; in the collateral Kota and Jabalpur stages of the Upper Gondwana they are as important an element in the flora as the cycads, while in the succeeding Umia stage they actually dominate the flora. Satpura and Central Provinces Jabalpur stage—Upper Gondwana rocks, of an altogether different facies of composition from that at Rajmahal, are developed on a very large scale in these areas. The base of the series rests unconformably on the underlying Maleri beds locally known under the name of Denwa and Bagra beds, and successively covers, by overlapping, all the older members of the Middle and Lower Gondwanas exposed in the neighbourhood. The rocks include two stages: the lower Chaugan and the upper Jabalpur stage. The Chaugan stage consists of limestones, clays and sandstones, with boulder conglomerates. I t is succeeded unconformably by the next stage, named after the town of Jabalpur. The rock components of the Jabalpur stage are chiefly soft massive sandstones and white or yellow shales, with some lignite and coal seams, and in addition a few limestone bands. The Jabalpur stage is of palaeontological interest because of its having yielded a rich Jurassic flora, rather distinct from th at of the preceding series and of somewhat newer age, viz. Lower Oolite. I t differs from the Rajmahal flora mainly in its containing a greater proportion of conifers, viz. Elatocladus (several species), Retinosporites, Brachyphyllum, Pagiophyllum, Desmiophyllum, Araucarites, Strobilites, and in the much reduced number of cycads. At Jabalpur this stage is overlain by the Lameta group of Cre­ taceous strata, remarkable for their containing many fossil remains of dinosaurs.

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145

Godavari Basin Kota stage_A narrow triangular patch of Upper Gondwana rocks occurs in the Godavari valley south of Chanda. The rocks are of the same type as those of the Satpuras, with the exception of the top member, which is highly ferruginous in its constitution. At places the oxides of iron are present to such an extent as to be of economic value. Here also two stages are recognised : the lower Kota stage, some 2000 feet in thickness, and the upper Chikiala stage, about 500 feet, com­ posed of highly ferruginous sandstones and conglomerates. The Kota stage is fossiliferous, both plant and animal remains being present in its rocks in large numbers. The Kota stage, which overlies the Maleri stage described above, consists of loosely consolidated sandstone, with a few shale beds and with some limestones. From the last beds numerous fossils of reptiles, fish, and crustacea have been obtained, e.g. several species of Lepidotus, Tetragonolepis, Dapedius, Ceratcdus ; and the reptiles Hyperodapedon, Pachygonia, Belodon, Parasuclius, Massospondylus, etc. The plants include the conifers Palissya, Araucarites and Cheirolepis, and numerous species of cycads belonging to Cycadites, Ptilophyllum, Taxites, etc., resembling the Jabalpur forms. The Chikiala stage is unfossiliferous, being often strongly ferruginous (haematitic) and conglomeratic. Gondwanas of the East Coast The Coastal system—Along the Coromandel coast, between Vizagapatam and Tanj or, there occur a few small isolated outcrops of the Upper Gondwanas along a narrow strip of country between the gneissic country and the coast-line. These patches are composed, for the most part, of marine deposits formed not very far from the coast, during temporary transgressions of the sea, containing a mingling of marine, littoral organisms with a few relics of the plants and animals that lived near the shore. Near the Peninsular mainland there are consequently to be seen in these outcrops both fossil plants of Gondwana facies and the marine or estuarine molluscs including ammonites. In geological horizon the different outliers correspond to all stages from the Raj­ mahal to the uppermost stage (Umia). E-ajahmundri outcrop—The principal of these outcrops is the one near the town of Rajahmundri on the Godavari delta. It includes three divisions : Tripetty sandstone—150 feet. Raghavapuram shales—150 feet. Golapili sandstones—300 feet.

1*6

GEOLOGY OF IN D IA

T H E U P P E R G O ND W A NA SYSTEM

This succession of beds rests unconformably over strata of Raniganj horizon, termed Chintalpudi sandstones. Lithologically they are composed of littoral sandstones, gravel and conglomerate rock, with a few shale-beds. The latter contain some marine lamellibranchs (e.g. species of Trigonia, including T. ventricosa) and a few species of ammonites. Intercalated with these are some beds containing impressions of the leaves of cycads and conifers. Ongole outcrop—Another outcrop of the same series of beds is found near the town of Ongole, on the south of the Kistna. I t also consists of three sub-divisions, all named after the localities :

m acm oliaceous dicotyledon and the flower of Williamsonia sewardi from the Rajmahal series (the flora of which is essentially identical with th at of the coastal Gondwanas) by Sahni lends support to the inference that both the series are probably of Neocomian or still later

Pavaloor beds—red sandstone. Vemavaram beds—shales. Budavada beds—yellow sandstone. The Vemavaram shales contain a very rich assemblage of Gondwana plants, related in their botanical affinities to the Kota and Jabalpur plants. Madras group—A third group of small exposures of the same rocks occurs near Madras, in which two stages are recognised. The lower beds form a group which is known as the Sripermatur beds, consisting of whitish shales with sandy micaceous beds containing a few cephalopod and lamellibranch shells in an imperfect state of preservation; the plant fossils obtained from beds associated in the same horizon correspond in facies to the Kota and Jabalpur flora. The Sripermatur beds are overlain by a series of coarser deposits, consisting of coarse conglomerates interbedded with sandstones and grits, which contain but few organic remains. This upper division is known as the Sattavadu beds. One more exposure of the same nature, occurring far to the north on the Mahanadi delta, is seen at Cuttack. I t is composed of grits, sandstones and conglomerates with white and red clays. The sand­ stone strata of this group are distinguished as the Athgarh sandstones. They possess excellent qualities as building stones, and have furnished large quantities of building material to numerous old edifices and temples, of which the temple of Jagan Nath Puri is the most famous. A middle Jurassic age was ascribed to these coastal Gondwanas but of late the discovery of a suite of better preserved ammonites from Budavada and Raghavapuram proves a considerably newer horizon for these beds, Lower Cretaceous (Barremian). The ammonites are : Holcodiscus, Lytoceras, Gymnoplites and Hemihoplites. The identification of angiospermous fossil wood Homoxylon, a

age*

147

y -

Umia Series

v•

Upper Gondwanas of Cutch—The highest beds of the Upper Gond­ wanas are found in Cutch, at a village named Umia. They rest on the top of a thick series of marine Jurassic beds (to be described with the Jurassic rocks of Cutch in a later chapter). The Umia series, as the whole formation is called, is a very thick series of marine conglomer­ ates, sandstones and shales, in all about 3000 feet in thickness. The special interest of this group lies in the fact th at with the topmost beds of this series, containing the relics of various cephalopods and lamellibranchs, there occur interstratified a number of beds contain­ ing plants of Upper Gondwana facies, pointing unmistakably to the prevalence of Gondwana conditions at the period of deposition of this series of strata. The marine fossils are of uppermost Jurassic to lower Cretaceous affinities, and hence serve to define the upward stratigraphic limit of the great Gondwana system of India within very pre­ cise bounds. The Umia plant-remains are thought to be the newest fossil flora of the Gondwana system. The following is the list of the important forms : (Conifers) Elatocladus, Retinosporites, Brachyphyllum, Pagiophyllum, Araucarites. (Cycads) Ptilophyllum, Williamsonia, Taeniopteris. (Ferns) Cladophlebis. Some of the species of these genera are allied to the Jabalpur species, others are distinctly newer, more highly evolved types. The Umia beds have also yielded the remains of a reptile, a species belonging to the famous long-necked Plesiosaurus of the European Jurassic. I t is named P. indica. In Northern Kathiawar there is a large patch of Jurassic rocks occupying the country near Dhrangadhra and Wadhwan which corresponds to the Umia group of Cutch in geological horizon. It has yielded conifers and cycads resembling the Umia plants. Economics—The Upper Gondwana rocks include several coalseams, but they are not worked. Some of its fine-grained sandstones, e g. those of Cuttack, are much used for building purposes, while the

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clays obtained from some localities arc utilised for a variety of cer­ amic manufactures. The soil yielded by the weathering of the Upper Gondwanas, as of nearly all Gondwana rocks, is a sandy shallow soil of poor quality for agricultural uses. Hence outcrops of the Gond­ wana rocks are marked generally by barren landscapes or else they are covered with a thin jungle. The few limestone beds are of value for lime-burning, while the richly haematitic or limonitic shales of some places are quarried for smelting purposes. The coarser grits and sandstones are cut for millstones.

R EFE R E N C E S W. T. Blanford, The A ncient Geography of Gondwanaland, Rec. G .S.I. vol. xxix. pt. 2, 1896. Charles Schuchert and Bailey Willis, Gondwana Land Bridges and Isthm ian Links, Bulletin of the Geological Society of America, vol. xliii., 1932. 0 . Feistm antel, The Fossil Flora of the Gondwana System, vols. i.-iv. Pal. Indica, 1879-1886. The Coal-Fields of India, Mem. G .S.I. vol. xli. p t. 1, 1913. T. H. Huxley, R. D. Lydekker, etc., Fossil V ertebrata of Gondwana System, Pal. Indica, Series IV. pts. 1-5 (1865-1885). G. de P. Cotter, Revised Classification of the Gondwana System, Rec. G .S.I. vol. xlviii. pt. 1, 1917. A. C. Seward and B. Sahni, Indian Gondwana P la n ts : A Revision, Pal. Indica, vol. vii. mem. 1, 1920. B. Sahni, Revisions of Indian Fossil Plants, Pal. Indica, N.S. vol. ix., 1928-1931 and vol. xx, mems. 2 and 3, 1932. C. S. Fox, The Gondwana System and Coal Deposits o f India, Mems. G .S.I. vols. lvii-lix., 1931-1934. H. Crookshank, Gondwanas of N orth Satpura, Mem. G .S.I. vol. lxvi. pt. 2, 1936.

CHAPTER XI U P P E R CARBONIFEROUS AND PERM IA N SYSTEMS

The commencement of the Aryan era—In the last two chapters we have followed the geological history of the Peninsula up to the end of the Jurassic period. Now let us turn back to the other provinces of the Indian region where a different order of geological events was in progress during this long cycle of ages. As referred to before, the era following the Middle Carboniferous was an era of great earth-movements in the extra-Peninsular parts of India, by which sedimentation was interrupted in the various areas of deposition, the distribution of land and sea was readjusted, and numerous other changes of physical geography profoundly altered the face of the continent. As a consequence of these physical revolutions there is, almost everywhere in India, a very marked break in the continuity of deposits, represented by an unconformity at the base of the Permo-Carboniferous system of strata. Before sedimentation was resumed, these earth-movements and crustal re-adjustments had resulted in the easterly extension over the whole of Northern India, Tibet and China of the great Mediterranean sea of Europe, which in fact at this epoch girdled almost the whole earth as a true mediter- * ranean sea, separating the great Gondwana continent of the south from the Eurasian continent of the northern hemisphere. The south­ ern shores of this great sea, which has played such an important part in the Mesozoic geology of the whole Indian region—the Tethys—• coincided with what is now the central chain of snow-peaks of the Himalayas, beyond which it did not transgress to any e x te n t; but, to the east and west of the Himalayan chain, bays of the sea spread over areas of Upper Burma and Baluchistan, a great distance to the south of this line, while an arm of the same sea extended towards the Salt-Range and occupied that region, with but slight interruptions, almost up to the end of the Eocene period. I t is in the zone of deepwater deposits that began to be formed on the floor of this Central sea at this time that the materials for the 'geological history of those 149

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] 51

regions are preserved for the long succession of ages, from the begin­ ning of the Permian to the middle of the Eocene period,'constituting the great Aryan era of Indian geology. ^ The nature of geosynclines—Portions of the sea-floor subsiding in the form of long narrow troughs concurrently with the deposition of sediments, and thus permitting an immense thickness of deep-water deposits to be laid down over them without any intermission, are called Geosynclines. It is the belief of some geologists that the slow continual submergence of the ocean bottom, which renders possible the deposition of enormously thick sediments in the geosynclinal tracts, arises, in the first instance, from a disturbance of the isostatic conditions of that part of the crust, further accentuated and enhanced by the constantly increasing load of sediments over localised tracts. The adjacent areas, on the other hand, which yield these sediments, have a tendency to rise above their former level, by reason of the constant unloading of their surface due to the continued exposure to the denuding agencies. They thus remain the feeding-grounds for the sedimentation-basins. This state of things will continue till gravity has restored the isostatic equilibrium of the region by a sufficient amount of deposition in one area and denudation in the other. At the end of this cycle of processes, after prolonged intervals of time, a reverse kind of movement will follow in this flexible and comparatively weak zone of the crust, rendered more plastic by the rise of the isogeotherms, compressing and elevating these vast piles of sediments into a mountain-chain, on the site of the former geosyncline. Geosynclines are thus long narrow portions of the earth’s outer shell which are relatively the weaker parts of the earth’s circumference, and are liable to periodic alternate movements of depression and elevation. It is such areas of the earth which give rise to the mountain-chains when they are, by any reason, subjected to great lateral or tangential compression. Such a compression occurs, for instance, when two large adjacent blocks of the earth’s crust—horsts—are sinking towards the earth’s centre during the secular contraction of our planet, consequent upon its continual loss of internal heat. The bearing of these conceptions on the elevation of the Himalayas, subsequent to the great cycle of Permo-Eocene deposits on the northern border of India, is plausible enough. The Himalayan zone is, according to this view, a geosynclinal tract squeezed between the two large continental masses of Eurasia and Gondwanaland. This subject is, how­ ever, one of the unsettled problems of modem geology, and one which is yet subjudice, and is, therefore, beyond the scope of this book. The records of the Himalayan area which we have now to study reveal an altogether different geological history from what we have known of the Gondwana sequence. I t is essentially a history of the oceanic area of the earth and of the evolution of the marine forms of life, as the latter is a history of the continental area of the earth and of the land plants and animals th at inhabited it. This difference

__

F.— Fault, usually reversed. Middle Productus Limestones.

Trias' Upper Productus beds.

153

emphasises the distinction between the stable mass of the Peninsula and the flexible, relatively much weaker extra-Peninsular area subject to the periodic movements of the crust. In contrast to the Peninsular horst, the latter is called the geosynclinal area. The Upper Carboniferous and Permian—The Upper Carboniferous and Permian systems are found perfectly developed in two localities of extra-Peninsular India, one in the western part of the SaltRange and the other in Kashmir and the northern ranges of the Himalayas.

13

— (Probable line of overthrust.)— Sa|ina series

C A R BO N IFE R O U S A N D P E R M IA N SYSTEM S

I. UPPER CARBONIFEROUS AND PERMIAN OF THE SALT-RANGE After the Salt-pseudomorph shale of the Cambrian age, the next series of deposits that was laid down in the Salt-Range area belongs to this system. Since the Cambrian, the Salt-Range, in common with the Peninsula, remained a bare land area exposed to denudational agencies, but, unlike the Peninsula, it was brought again within the area of sedimentation by the late Carboniferous movements. From this period to the close of the Eocene, a branch of the great central sea to the north spread over this region and laid down the deposits of the succeeding geological periods, with a few slight interruptions. These deposits are confined to the western part of the Range, beyond longitude 72° E., where they are exposed in a series of more or less parallel and continuous outcrops running along the strike of the range. In the eastern part of these mountains, PermoCarboniferous rocks are not met with at all, the Cambrian group being there abruptly terminated by a fault of great throw, which has thrust the Nummulitic limestone of Eocene age in contact with the Cambrian. The Permo-Carboniferous rocks of the western Salt-Range are a thick series of highly fossiliferous strata. A two-fold division is dis­ cernible in them : a lower one composed of sandstones, and an upper one mainly of limestones, characterised by an abundance of the braehiopods Productus, and hence known as the Productus limestone. The Productus limestone constitutes one of the best developed geo­ logical formations of India, and, on account of its perfect develop­ ment, is a type of reference for the Permian system of the other parts of the world.

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The table below shows the chief elements of the Permo-Carboniferous system of the Salt-Range :

the Malani rhyolites, felsites and granites of Vindhyan age—an im­ formation of Rajputana. These are intermixed with smaller pebbles from various other crystalline rocks of the same area, and embedded in a fine dense matrix of clay. Besides striations and polishing, a certain percentage of the pebbles and boulders shows distinct “ facetting ”. The Aravalli region must have been the home of snow-fields nourishing powerful glaciers at this time, as the size of the boulders as well as the distances to which they have been trans­ ported from their source clearly testify to the magnitude of the glaciers radiating from it. Boulder-beds similar to that of the Salt-Range, and also like them composed of ice-borne boulders of Malani rhyolites and other crystal­ line rocks, are found in Rajputana in Marwar (Jodhpur State) and are known as the Bap and Pokaran beds, from places of that name. At the latter place there occur typical roches moutonnees. The Talchir boulder-bed is homotaxial with the glacial beds associated with the Eurydesma beds of South East Australia. The Speckled sandstones—The boulder-bed is overlain by a group of olive shales and sandstones forming the lower part of the Speckled sandstone series designated as the Conularia beds, because of their containing the fossil Conularia enclosed in calcareous concretions. The genus Conularia is of doubtful systematic position and, like Hyolithes, is referred to the Pteropoda, or at times to some other sub­ order of the Gastropoda, or even to some primitive order of the Cephalopoda. Associated fossils are, Pleurotomaria, Eurydesma, Bucania, Nucula, Pseudomonotis, Chonetes, Aviculopecten, etc. These fossils are of interest because of their close similarity to the fauna of the Permo-Carboniferous of Australia, which also contains, intercalated at its base, a glacial formation in every respect identical to that of the Talchir series. The Conularia beds are succeeded by a series of mottled or speckled red sandstones, from 300 to 500 feet in thickness, interbedded with red shales. The whole group is currentbedded, and gives evidence of deposition in shallow water. From the mottled or speckled appearance of the sandstone, due to a variable distribution of the colouring peroxide ofrron, the group is designated the Speckled sandstones. The Productus limestone—This group is conformably overlain by the Productus limestone, one of the most important formations of India, and one which has received a great deal of attention from Indian geologists, being the earliest fossiliferous rock-system dis­ covered in India. I t is fully developed in the central and western p o rta n t

Chideru Stage. Marls and sandstones. Upper Kundghat „ Sandstones with Bel2 0 0 ft. 1 lerophons. Jabi „ Sandy limestones. f Kalabagh Middle 300 ft, 1 Virgal

Productus limestone 700 ft.

f Katta Lower 2 0 0 ft.

f

Amb

Thuringian.

Crinoidal limestones with marls and dolo­ Punjabian. mites. Cherty limestones. Brown sandy lime­ stones. Calcareous sandstones. PermoFusulina limestone. Carboniferous.

Speckled sandstones, 300 ft. Conularia beds, 2 0 0 ft.

Clays, grey and blue. Upper Mottled sandstones. Carboni­ Olive shales and sand­ ferous. stones. Speckled Conularia and Eurysandstones desma. 700 ft. Boulder 1 Uralian. bed, Talchir Stage Glaciated boulders in 10-200 a fine matrix. ft. Boulder beds—The basement bed of the series is a boulder-conglomerate of undoubted glacial origin, which from its wide geographical occurrence in strata of the same horizon, in such widely separated parts of India as Hazara, Simla, the Salt-Range, Rajputana, Orissa and various other localities wherever the Lower Gondwana rocks have been found, has been made the basis of an inference of a Glacial Age at the commencement of the Upper Carboniferous period throughout India. The evidence for this Ice Age in India lies in the existence of the characteristic marks of glacial action in all these areas, viz. beds of compacted “ boulder-clay ” or glacial drift, resting upon an under surface which is often sharply defined by being planed and striated by the glaciers. The most striking character of a boulder-clay is its heterogeneity, both in its component materials, which have been transported from distant sources, and in the absence of any assort­ ment and stratification of these materials. Many of the boulders in the boulder-bed of the Salt-Range are striated and polished blocks of

155

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part of the range, but thins out at its eastern end. About 700 feet of limestones are exposed in a series of fine cliffs near the Nilawan valley, and thence continue westwards along the Salt-Range right up to the Indus gorge, beyond which the group disappears gradually. The best and the most accessible outcrops of the rocks are in the Warcha valley 1 and Chideru hills in the neighbourhood of Musa Khel, west of the Son Sakesar plateau. The greater part of the Productus lime­ stone is a compact, crinoidal magnesian limestone sometimes passing into pure crystalline dolomite, associated with beds of marl and sand­ stones. I t contains a rich and varied assemblage of fossil brachiopods, corals, crinoids, gastropods, lamellibranchs, cephalopods, fusulinae and plants, constituting the richest Upper Palaeozoic fauna anywhere dis­ covered in India, to which the faunas of the other homotaxial deposits are referred. The abundance and variety of the Productus fauna has thus led to the name of Punjabian being given to the series of Middle Permian strata coming between the Artinskian and Thuringian. The stage name of Punjabian has also been used in the past to include the strata from the Boulder-bed to the top of the Speckled sandstone (Uralian to Artinskian). On a palaeontological basis the Productus limestone is divided into three sections: the Lower, Middle and Upper. With the lower beds of the Lower Productus limestone there comes a sudden change in the character of the sediments, accompanied by a more striking change in the facies of the fauna, almost all the species of the Speckled sandstone group disappearing from the overlying group. The lower 200 feet carry many beds of Fusulina limestone with Parafusulina. I t is composed of soft calcareous sandstones, full of fossils, with coal-partings a t the base. Productus cora, P. semireticulatus and P. spiralis are the characteristic species of this division. Associated with these, in the coal-partings, are the genera Glossop­ teris and Gangamopteris, of Damuda affinities. I t includes two stages : the lower, more arenaceous stage is well seen at the Amb village, and is known as the Amb beds; and the upper calcareous stage is known as the K atta beds. The Middle is the thickest and most characteristic part of the Pro­ ductus limestone, consisting of from 2 0 0 to 300 feet of blue or grey limestone, which forms the high precipitous escarpments of the mountains near Musa Khel. Dolomite layers, which are frequent, are white or cream-coloured, and from the greater tendency of dolomite ,to occur in crystalline form they are much less fossiliferous owing to 1 Records, 0.8.1. vol. lxii, pt. 4, 1930.

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the obliteration of the fossils attending the recrystallisation process. Marly beds are common, and are the best repositories of fossils, yield­ ing them readily to the hammer. The limestones are equally fossili­ ferous, but the fossils are very difficult to extract, being only visible in the weathered outcrops at the surfaces. Many of the fossils are silicified, especially the corals. There is also an intercalation of plantbearing Lower Gondwana shales and sandstones. P. lineatus is a common brachiopod species in the Middle Productus. Flint and chert concretions are abundantly distributed in the limestones. This division also includes two stages, Virgal and Kalabagh, the latter containing the ammonoids Xenaspis and Foordoceras. The Upper Productus group is much less thick, hardly reaching 100-200 feet at places. The group is more arenaceous, being composed of sandstones with carbonaceous shales, with subordinate bands of limestone and dolomite. Silica is the chief petrifying agent here also. P. indicus is a common species. Fossils are numerous, but they reveal a striking change in the fauna, which separates this group from the preceding group. The most noteworthy feature of this change is the advent of cephalopods of the order Ammonoidea, represented by a number of its primitive genera. The topmost stage of the Upper Productus forms a separate stage by itself, known as the Chideru beds. They show a marked palaeontological departure from the underlying ones in the greatly diminished number of brachiopods and the increase of lamellibranchs and cephalopods. They are thus to be regarded, from these peculiarities, as a sort of transition, or “ passage beds” , be­ tween the Permian and the Triassic. The Chideru beds pass con­ formably and without any notable change into a series of Ceratite- j bearing beds of Lower Triassic age. Productus fauna—The following is a list of the more characteristic genera of fossils belonging to the Productus limestone. Many of the genera are represented by a large number of species : Upper Productus : (Ammonites) Xenodiscus, Cyclolobus, Medlicottia, Arcestes, Sageceras, Popanoceras, Taenioceras ; (Brachiopods) Productus, Oldhamina, Derbya, Chonetes, Martinia, Aulostegia ; (Gastropods) Bellerophon, Euphemus, e tc .; (Lamellibranchs) Schizodus, Lima, Gervillia; (Polyzoa) Entolis, Synocladia, etc. Middle Productus : (Brachiopods) Productus, Spirifer, Spiriferina, Athyris, Lyttonia, Oldhamina, Richthofenia, Reticularia, Hemyptychina ; (Lammellibranchs) Oxytoma, Pseudtomonotis, Marginifera, Notothyris; (Polyzoa) Fenestella, Stenopora,

GEOLOGY OF IN D IA

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Thamniscus, Acanthocladia; (Worm) Spirorbis; (Corals) Zaphrentis, Lonsdaleia ; (Gastropods) Macrocheilus ; (Cephalo­ poda) Xenaspis, Nautilus, Orthoceras. Lower Productus : Productus (P. cora, P. semireticulatus, P. spiralis) Spirifer, Spiriferina, Athyris royssi, Orthis, Reticularia, Richthofenia, Martinia, Dielasma, Streptorhynchus, Strophalosia ; (Foraminifers) Fusulina, Parafusilina. [Besides these mentioned above, the following fossils also are char­ acteristic of the Salt-Range Productus limestone : Gastropods : Buomphalus, Macrocheilus, Naticopsis, Phaseonella, Pleurotomaria, Murchisonia, Bellerophon (Bucania, Stachella, Euphemus, and several other genera of the family Bellerophontidae), Hyolithes and Entalis. Lamellibranchs : Cardiomorpha, Lucina, Cardinia, Schizodus, Aviculopecten, Pecten (two species). Brachiopods : These are the most abundant, both as regards species and individuals. Dielasma is represented by ten species, Notothyris (eight species), Lyttonia (three species), Camarophoria (five species), Spirigerilla (ten species), Athyris (ten species), Spirifer (eight species), Martiniopsis, Martinia, Reticularia, Orthis, Strophomena, Streptorhynchus, Derbya (eight species), Leptaena, Chonetes (fourteen species), Strophalosia, Productus (fifteen species), and Marginifera. Polyzoa : Polypora, Goniocladia, Thamniscus, Synocladia. Crinoids : Poteriocrinus, Philocrinus, Cyathocrinus, etc. Corals : Pachypora, Michelinia, Stenopora, Lonsdaleia, Amplexus, Zaphrentis, Clisiophyllum. Ganoid and other fishes. Plants, etc.]

The Anthracolithic systems of India—The lower part of the Saltftange Productus limestone group is, from fossil evidence, the homotaxial equivalent of the Permo-Carboniferous of Kashmir, Spiti and Northern Himalayas generally. The term “ anthracolithic”, used by some authors as a convenient term to express the closely connected Carboniferous and Permian systems of rocks and fossils in those areas, e.g. the Shan States of Burma, which exhibit an intimate stratigraphic as well as palaeontological connection with one another, and where it is difficult to separate the Carboniferous from the Permian, is to be distinguished from the term “ Permo-Carboni­ ferous ”, which refers to the zone of strata lying between the top­ most Carboniferous and the base of the Permian. vX*

158

The Productus fauna shows several interesting peculiarities. While the fauna as a whole is decidedly Permian, the presence in it of several genera of true Ammonites and of a lamellibranch like Oxytoma and a Nautilus species, which in other parts of the world are not met with in rocks older than the Trias, gives to it a somewhat newer aspect. The most noteworthy peculiarity, however, is the association of such eminently Palaeozoic forms as Productus, Spirifer, Athyris, Bellerophon, etc., with cephalopods of the order Ammonoidea. All forms which can be regarded as transitional between the goniatites and the Triassic ceratites are found, including true ammonites like ^/Jyclolobus, Medlicottia, Popanoceras, Xenodiscus, Arcestes, etc. / Some of these possess a simple pattern of sutures resembling those of the Goniatites (sharply folded) or Clymenia (simple zig-zag lobes and saddles), while others show an advance in the complexity of the sutures approaching those of some Mesozoic genera.

159

n . THE UPPER CARBONIFEROUS AND PERMIAN SYSTEMS OF THE HIMALAYAS The Himalayan representatives of the Productus limestone are developed in the northern or Tibetan zone of the Himalayas along their whole length from Kashmir to Kumaon and beyond to the Everest region. They are displayed typically at two localities, Spiti and Kashmir, where they have been studied in great detail by the Geological Survey of India. Spiti In Chapter V III we have followed the Palaeozoic sequence of the area up to the Fenestella shales of the Po series. Resting on the top of the Fenestella shales, in our type sections, but at other places lying over beds of varying horizons from the Silurian to the Carboniferous, is a conglomerate layer of variable thickness, belonging in age to the Upper Carboniferous or Permian. This conglomerate, as has been stated before, is an important datum-line in India, for it is made the basis of the division of the fossiliferous rock-systems of India into two major divisions, the Dravidian and Aryan. The Aryan era, therefore, commences in the Himalayas, with a basement conglomerate, as it commenced in the Salt-Range and in the Peninsula with the glacial boulder-bed. * The Productus shales—The conglomerate is succeeded by a group of calcareous sandstones, containing fossil brachiopods of the genera Spirifer, Productus, Spiriferina, Dielasma and Streptorhynchus, repre­ senting the Lower Productus horizon of the Salt-Range. These are

GEOLOGY OF IN D IA

overlain by a thin group of dark carbonaceous shales, the charac­ teristic Permian formation of the Himalayas, known as the Productus shales, correspond­ ing to the Upper Productus horizon. (See Figs. 1 1 and 19.) The Productus shales are a 43 Ol r-® . group of black siliceous, mica­ Kft 2 «■“ « ceous and friable shales. They ^s .a J ■§58 are only 1 0 0 to 2 0 0 feet in I §g^'& thickness, but are distinguished by a remarkable constancy in their lithological composition over the enormous extent of a, mountains from Kashmir to Oh p Nepal. The Productus shales constitute one of the most conspicuous and readily dis­ tinguished horizons in the Palaeozoic geology of the Himalayas. Being a soft, earthy deposit, it has yielded most to the severe flexures and compression of this part of the mountains and suffered a greater degree of crushing than the more rigid strata above and below. (See Plate VIII facing p. 114, also Plate X II Ja ^ • facing p. 166.) The fossil a ®■£* eS organisms entombed in the ' _ ® - • T ! 3 fa-S shales include characteristic TJ 'Z %8 Permian brachiopod species (2(5,3! of Productus (P. purdoni), Spirifer (S. musakheylensis, S. rajah, and five other species), Spirigera, Dielasma, Martinia, Marginifera (M . himalayensis) and Chonetes. Of these the species Spirifer rajah and Marginifera himalayensis are highly characteristic of the Permian •E

® I 'D

CQ

X I.

I

PLATE

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of the Central Himalaya. In some concretions contained in the Mack shales arc enclosed ammonites like Xenaspis and Cyclolobus. The Permian rocks of the Central Himalaya have been also designated as the Kuling system from a locality of that name in the Spiti valley. Dr. Hayden gives the following sequence of Permian strata in the Spiti area : Lower Trias. Otoceras zone of Lower Trias. Productus shales : black or brown siliceous shale with Xenaspis, Cyclolobus, Marginifera himalayensis, etc. Permian. Calcareous sandstone with Spirifer. Grits and quartzites. Conglomerates (varying in thickness). Slight unconformity ---------------------------Upper Carboniferous. Fenestella shales of Po series. The Productus shales are succeeded by a group of beds character­ ised by the prevalence of the Triassic ammonite Otoceras, which de­ notes the lower boundary of the Trias of the Himalayas, one of the most important and conspicuous rock-systems of the Himalayas from the Pamirs to Nepal. The strata above described mark the beginning of the geosyn­ clinal facies of deposits constituting the northern or Tibetan zone of the Himalayas. As yet the strata are composed of shales and sand­ stones, indicating proximity of the coast and comparatively shallow waters, but the overlying thick series of Triassic and Jurassic systems are wholly constituted of limestones, dolomites and calcareous shales of great thickness, giving evidence of the gradual deepening of the ocean bottom. Kashmir In keeping with the rest of the Palaeozoic systems, the Upper Carboniferous and Permian is developed on a large scale in Kashmir. The Upper Carboniferous consists of a thick (over 8000 feet) volcanic series—Panjal Volcanic series—of bedded tuffs, slates, ash-beds and andesitic to basaltic lava-flows (Panjal Trap). The slaty tuffs con­ tain at places marine fossils allied to the fauna of the Productus lime­ stone. In the Tertiary zone of the Kashmir Outer Himalaya there occur a number of large masses of an unfossiliferous dolomitic lime­ stone, laid bare as cores of denuded anticlines, in the Upper Tertiaries of Murree age. This limestone (the “ Great limestone ” of

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Medlicott) is markedly similar in it 3 lithological characters and stratigraphic relations to the “ Infra-Trias ” limestone of Sirban, Hazara, and is now referred to it. This limestone is of considerable economic value from some workable lodes of zinc, copper and nickel occurring in it (p. 352). A most interesting circumstance in connec­ tion with the Permian of Kashmir is the association of both the Gond­ wana facies of fluviatile deposits containing seed-ferns like Gangamop­ teris and Glossopteris and the marine facies containing the character­ istic fossils of the age. The Gondwana beds (known as the Gavgamopteris beds), which are the local representatives of the TaichirDamuda series of the Peninsula, are overlain by the marine Permian beds (Zewan series), containing a brachiopod fauna identical in many respects with that of the Productus limestone. (Chap. XXVII, p. 416). Hazara As in the western parts of Kashmir, the Palaeozoic record of Hazara is confined to representatives of the Upper Carboniferous and the Permian. On the upturned truncated edges of Purana slates, the contemporaries of Attock and Dogra slates, there comes a boulderconglomerate composed of facetted and striated boulders set in a fine silty matrix. This boulder-bed (tillite), regarded as the contemporary of the Talchir and Salt-Range glacial conglomerate, is followed by a series of purple and speckled sandstones and shales, the whole overlain by dolomitic limestones, over 2000 feet in thickness. The lime­ stone is compact and well bedded, of purple, grey and cream colours ; its weathering is very peculiar, giving rise to blocks with deeply in­ cised cuts and grooves. The rock is wholly unfossiliferous, but from its intimate association in Kaghan with the Panjal Volcanic series and the occurrence of the glacial boulder-bed at its base there is now little room for doubting its Upper Carboniferous or Permo-Carboniferous age. The above Hazara sequence was formerly regarded as probably Devonian and named “ Infra-Trias ” from its immediately underlying the more conspicuous Trias limestone of the Sirban moun­ tain, a prominent mountain near Abbottabad. (Fig. 2 2 .) Simla Hills Area With the exception of some intervening limestones and slates of uncertain position (Shali limestone), the system of deposits which comes next above the Simla slates is referred to the Upper Carboni­ ferous and Permian with a high degree of probability. As in Hazara,

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the bottom bed i3 a glacial boulder-bed—the Blaini conglomerate— unconformably reposing on the Simla slates or the Jaunsars, suc­ ceed ed by pink-coloured dolomitic limestones. Over these comes a thick series of carbonaceous shaly slates, with brown quartzite partingS__the Infra-Krol series—which have been provisionally corre­ lated with the Lower Gondwanas of the Peninsula. The succeeding series consists of a thick group of massive blue limestones and shales, underlain by partly-consolidated, coarse sandstones, referred to as the Krol series, from their building the conspicuous mountain of that name near Solon. As with the rest of the formations of the Simla area, the Krol limestones, so eminently adapted to preserve any entombed organisms, are entirely barren of fossils. The inference that it is homo­ taxial with the Sirban limestone of Hazara and with the Productus group of the Salt-Range is based on the probable parallelism of the sequence commencing with a glacial boulder-bed (? Talchir) in these areas. The most prominent development of the Krol series is in what is known as the Krol belt of the Outer Himalaya of Simla, extending from near Subathu to Naini Tal, a distance of 180 miles. A very perfect stratigraphic sequence has been worked out in this area by J. B. Auden, which has revealed the presence of a number of thrusts causing overriding of Tertiary rocks by the much older rocks we are considering here. In the neighbourhood of Solon and Subathu, Eocene and Oligocene rocks are exposed as inliers (“ window's ”) by the erosion of the superjacent overthrust masses of these presumed Permo-Carboniferous rocks. 1 Burma We have seen in Chapter V III th at there is in Upper Burma (Northern Shan States) a conformable passage of the Devonian and Carboniferous to strata of the Permian age in the great limestone formation constituting the upper part of what is known there as the Plateau limestone. (See also Fig, 1 2 , p. 117.) In the upper beds of these limestones there is present a fauna 2 of brachiopods, corals, polyzoa, etc., which show on the whole fairly close relations to the Productus limestone of the Salt-Range and the Productus shales of the Spiti Himalayas and the Zewan series of Kashmir. From these affinities between the homotaxial faunas of the Indo-Burma region, Dr. Diener, the author of many memoirs on the faunas, considers all * -Rec. G.S.I. vol. lxvii. pt. 4, 1934. 193^n^ raC°^^*C ^aunas

the Southern Shan States, Rec. G.S.I. vol. lxvii. pt. 1,

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of the Central Himalaya. In some concretions contained in the Mack shales are enclosed ammonites like Xenaspis and Cyclolobus. The Permian rocks of the Central Himalaya have been also designated as the Kuling system from a locality of that name in the Spiti valley. Dr. Hayden gives the following sequence of Permian strata in the Spiti area : Lower Trias. Otoceras zone of Lower Trias. Productus shales : black or brown siliceous shale with Xenaspis, Cyclolobus, Marginifera himaPermian. layensis, etc. Calcareous sandstone with Spirifer. Grits and quartzites. Conglomerates (varying in thickness). Slight unconformity ---------------------------Upper Carboniferous. Fenestella shales of Po series. The Productus shales are succeeded by a group of beds character­ ised by the prevalence of the Triassic ammonite Otoceras, which de­ notes the lower boundary of the Trias of the Himalayas, one of the most important and conspicuous rock-systems of the Himalayas from the Pamirs to Nepal. The strata above described mark the beginning of the geosyn­ clinal facies of deposits constituting the northern or Tibetan zone of the Himalayas. As yet the strata are composed of shales and sand­ stones, indicating proximity of the coast and comparatively shallow waters, but the overlying thick series of Triassic and Jurassic systems are wholly constituted of limestones, dolomites and calcareous shales of great thickness, giving evidence of the gradual deepening of the ocean bottom. Kashmir In keeping with the rest of the Palaeozoic systems, the Upper Carboniferous and Permian is developed on a large scale in Kashmir. The Upper Carboniferous consists of a thick (over 8000 feet) volcanic series—Panjal Volcanic series—of bedded tuffs, slates, ash-beds and andesitic to basaltic lava-flows (Panjal Trap). The slaty tuffs con­ tain at places marine fossils allied to the fauna of the Productus lime­ stone. In the Tertiary zone of the Kashmir Outer Himalaya there occur a number of large masses of an unfossiliferous dolomitic lime­ stone, laid bare as cores of denuded anticlines, in the Upper Tertiaries of Murree age. This limestone (the “ Great limestone ” of W.Q.I.

t,

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Medlieott) is markedly similar in its litliological characters and stratigraphic relations to the “ Infra-Trias ” limestone of Sirban, Hazara, and is now referred to it. This limestone is of considerable economic value from some workable lodes of zinc, copper and nickel occurring in it (p. 352). A most interesting circumstance in connec­ tion with the Permian of Kashmir is the association of both the Gond­ wana facies of fluviatile deposits containing seed-ferns like Gangamop­ teris and Glossopteris and the marine facies containing the character­ istic fossils of the age. The Gondwana beds (known as the Ganga­ mopteris beds), which are the local representatives of the TaichirDamuda series of the Peninsula, are overlain by the marine Permian beds (Zewan series), containing a brachiopod fauna identical in many respects with that of the Productus limestone. (Chap. XXVII, p. 416). Hazara As in the western parts of Kashmir, the Palaeozoic record of Hazara is confined to representatives of the Upper Carboniferous and the Permian. On the upturned truncated edges of Purana slates, the contemporaries of Attock and Dogra slates, there comes a boulderconglomerate composed of facetted and striated boulders set in a fine silty matrix. This boulder-bed (tillite), regarded as the contemporary of the Talchir and Salt-Range glacial conglomerate, is followed by a series of purple and speckled sandstones and shales, the whole overlain by dolomitic limestones, over 2000 feet in thickness. The lime­ stone is compact and well bedded, of purple, grey and cream colours ; its weathering is very peculiar, giving rise to blocks with deeply in­ cised cuts and grooves. The rock is wholly unfossiliferous, but from its intimate association in Kaghan with the Panjal Volcanic series and the occurrence of the glacial boulder-bed at its base there is now little room for doubting its Upper Carboniferous or Permo-Carboniferous age. The above Hazara sequence was formerly regarded as probably Devonian and named “ Infra-Trias ” from its immediately underlying the more conspicuous Trias limestone of the Sirban moun­ tain, a prominent mountain near Abbottabad. (Fig. 22.) i "

Simla Hills Area With the exception of some intervening limestones and slates of uncertain position (Shali limestone), the system of deposits which comes next above the Simla slates is referred to the Upper Carboni­ ferous and Permian with a high degree of probability. As in Hazara,

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163

the bottom bed is a glacial boulder-bed—the Blaini conglomerate— unconformably reposing on the Simla slates or the Jaunsars, suc­ ceeded by pink-coloured dolomitic limestones. Over these comes a thick series of carbonaceous shaly slates, with brown quartzite partings:—the Infra-Krol series—which have been provisionally corre­ lated with the Lower Gondwanas of the Peninsula. The succeeding series consists of a thick group of massive blue limestones and shales, underlain by partly-consolidated, coarse sandstones, referred to as the Krol series, from their building the conspicuous mountain of that name near Solon. As with the rest of the formations of the Simla area, the Krol limestones, so eminently adapted to preserve any entombed organisms, are entirely barren of fossils. The inference that it is homotaxial with the Sirban limestone of Hazara and with the Productus group of the Salt-Range is based on the probable parallelism of the sequence commencing with a glacial boulder-bed (? Talchir) in these areas. The most prominent development of the Krol series is in what is known as the Krol belt of the Outer Himalaya of Simla, extending from near Subathu to Naini Tal, a distance of 180 miles. A very perfect stratigraphic sequence has been worked out in this area by J. B. Auden, which has revealed the presence of a number of thrusts causing overriding of Tertiary rocks by the much older rocks we are considering here. In the neighbourhood of Solon and Subathu, Eocene and Oligocene rocks are exposed as inliers (“ windows ”) by the erosion of the superjacent overthrust masses of these presumed Permo-Carboniferous rocks. 1 Burma We have seen in Chapter V III th at there is in Upper Burma (Northern Shan States) a conformable passage of the Devonian and Carboniferous to strata of the Permian age in the great limestone formation constituting the upper part of what is known there as the Plateau limestone. (See also Fig, 12, p. 117.) In the upper beds of these limestones there is present a fauna 2 of brachiopods, corals, polyzoa, etc., which show on the whole fairly close relations to the Productus limestone of the Salt-Range and the Productus shales of the Spiti Himalayas and the Zewan series of Kashmir. From these affinities between the homotaxial faunas of the Indo-Burma region, Dr. Diener, the author of many memoirs on the faunas, considers all 1 Bee. O.S.I. vol. lxvii. pt. 4, 1934. 193:fnthraCOlithi° ^ aunas

t ^ie Southern Shan States, Bee. G.S.I. vol. lxvii. pt. 1,

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these regions as belonging to the same zoo-geographical province, their differences being ascribed to the accidents of environment, isola­ tion through temporary barriers and differences in the depth and salinity of waters, etc. The Permo-Carboniferous rocks of Burma contain two foraminiferal limestones : the Fusulina limestone and the Schwagerina lime­ stone, from the preponderance of these two genera of Carboniferous and Permian foraminifers.

1. Chaung-Magyi series (Cambrian). 2 and 3. Naungkangyi series (Ordovician). 4. Namshim beds (Silurian). 5. Plateau limestone (Devonian and Permo-Carboniferous). 6. Napeng beds (Upper Triassic). La Touche, Mem. G.S.I. xxxix. pt. 2, 1913.

HI. MARINE PERMO-CARBONIFEROUS OF THE PENINSULA An extraordinary occurrence has been recorded 1 at Umaria (Central India) of a thin and solitary band of marine Productus lime­ stone in the midst of fresh-water coal-bearing beds belonging to the Barakar stage of the Damuda series (Lower Gondwana system). The marine intercalation is only ten feet thick and conformably underlies the sandstone and grit strata of normal Barakar facies, exposed in a cutting in the Umaria coal-field. I t unconformably over­ lies the Talchir boulder-bed. The limestone bed is made up entirely of the fossil shells of Productus, the only other fossils present being Spiriferina, and Reticularia. Cowper Reed considers the Umaria fauna is quite local and unique, showing no clear affinities with the nearby Salt-Range province, but rather with the Himalayan and Russian Permo-Carboniferous pro­ vince. This bed must be regarded as a solitary record of an evanescent transgression of the sea-waters into the heart of the Peninsula, either from the North through Rajputana, or from the West Coast, induced 1Sinor. K- P.. Mineral Resources of Rewa State, p. 21, 1923.

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by some diastrophic modification of the surface of the land, which, however, must have been of a transient nature and must have soon ceased to operate. R EFER EN C ES H. H. Hayden, Geology of Spiti, Mem. G .S.I. vol. xxxvi. pt. 1, 1904. K arl Diener, Pal. Indica, Series XV. vol. i. pts. 2, 3, 4 and 5 (1897-1903); Pal. Indica, New Series, vol. iii. mem. iv. (1911); vol. v. mem. ii. (1915). WT. Waagen, Pal. Indica, Series X III. vol. i. pts. 1-7 (1879-1887), (Salt-Range F ossils); and vol. iv. pts. 1 and 2 (1889-1891).

CHAPTER X II

PLATE

General—The Productus shales (Ruling system) of the Himalayas and the Chideru stage of the Productus limestone of the Salt-Range are succeeded by a more or less complete development of the Triassic system. The passage in both cases is quite conformable and even transitional, no physical break in the continuity of deposits being observable in the sequence. The Triassic system of the Himalayas, both by reason of its enormous development in the northern geosyn­ clinal zone as well as the wealth of its contained faunas, makes a con­ spicuous landmark in the history of the Himalayas. The abundance of its cephalopodan fauna is such that it has been the means of a zonal classification of the system (zones are groups of strata of variable thickness, but distinguished by the exclusive occurrence, or predom­ inance, of a particular species, the zone being designated by the name of the species). In Spiti, Garhwal and Kumaon, and on the north­ west extension of the same axis in Kashmir, the Trias attains a de­ velopment of more than 3000 feet, containing three well-marked sub­ divisions, corresponding respectively to the Bunter, Muschelkalk and Keuper of Europe. Other regions where the Trias occurs, either completely developed or in some of its divisions, are the Salt-Range, Baluchistan and Burma. In the Salt-Range the Triassic system is confined to the Lower Trias and the lower part of the Middle Trias, while in Baluchistan and Burma it is confined to the Upper Triassic stages only. In the two latter areas it assumes an argillaceous facies of shales and slates, whereas in the Himalayan region the system is entirely composed of limestone, dolomites and calcareous shales. f Principles of classification of the geological record—With the Trias we \ enter the Mesozoic era of geology, and before we proceed further we might at this stage enquire into the basis for the classification of the geological record into systems and series, and consider whether the interruptions or “ blanks ” in the course of the earth’s history, which have led to the crea­ tion of the chief divisions, in the first instance, in some parts of the world, were necessarily world-wide in their effects and applicable to all parts of the world.

X II

T H E TRIASSIC SYSTEM

T H E TRIASSIC SYSTEM

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In Europe the geological record is divided into three broad section? or groups : the Palaeozoic, Mesozoic and Cainozoic, representing three great eras in the history of the development of life on the earth, each of which is separated from the one overlying it by an easily perceptible and compara­ tively wide-spread physical break or “ unconformity Whether these divisions, so well marked and natural in Europe, where they were first re­ cognised, are as well marked and natural in the other parts of the world, and whether these three, with their sub-divisions, should be the funda­ mental periods of earth-history for the whole world is a subject over which the opinion of geologists is sharply divided. In the geological systems of India, as in the other regions of the earth, although the distinctive features of the organic history of the Palaeozoic, Mesozoic and Cainozoic are clearly evident, as we ascend in the stratigraphic scale, we cannot detect the sharp breaks in the continuity of that history at which one great time-interval ends and the other begins. Just at these parts the geological record appears to be quite continuous in India, and any attempt at setting a limit would be as arbitrary as it would be unnatural. On the other hand, there are great interruptions or “ lost intervals ” in the Indian record at other stages (where the European record is quite continuous) at which it is much more natural to draw the dividing lines of its principal divisions—the groups. As we have already seen, Sir T. H. Holland has accomplished this in his scheme of the classification of the Indian formations. Though generally adopted in India, and best suited to the rather imperfect character of the geological record as preserved in India, such a classification and nomencla­ ture may not be acceptable to those geologists who hold that the grand divisions of geology are universal and applicable to the whole world. The subject is difficult to decide one way or the other, but for the information of the student the following view, which summarises the arguments of the latter, class of geologists with admirable lucidity, is given verbatim from the work of Professors T. C. Chamberlin and R. D. Salisbury : 1 “ We believe that there is a natural basis of time-division, that it is recorded dynamically in the profounder changes of the earth’s history, and that its basis is world-wide in its applicability. It is expressed in interrup­ tions of the course of the earth’s history. It can hardly take account of all local details, and cannot be applied with minuteness to all localities, since geological history is necessarily continuous. But even a continuous history has its times and seasons, and the pulsations of history are the natural basis for its divisions. “ In our view, the fundamental basis for geologic time-divisions has; its seat in the heart of the earth. Whenever the accumulated stresses within the body of the earth overmatch its effective rigidity, a readjustment takes place. The deformative movements begin, for reasons previously set forth, with a depression of the bottoms of the oceanic basins, by which their capacity is increased. The epicontinental waters are correspondingly withdrawn into them. The effect of this is practically universal, and all continents are affected in a similar way and simultaneously. This is the reason why the classification of one continent is also applicable, in its larger features, to another, though the configuration of each individual continent 1 Advanced Geology, vol. iii., Earth History.

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modifies the result of the change, so far as that continent is concerned. The far-reaching effects of such a withdrawal of the sea have been indicated repeatedly in preceding pages. Foremost among these effects is the pro­ found influence exerted on the evolution of the shallow-water marine life, the most constant and reliable of the means of intercontinental correlation. Second only to this in importance is the influence on terrestrial life through the connections and disconnections that control migration. Springing from the same deformative movements are geographic and topographic changes, affecting not only the land, but also the sea currents. These changes affect the climate directly, and by accelerating or retarding the chemical reactions between the atmosphere, hydrosphere, and lithosphere,'affect the constitu­ tion of both air and sea, and thus indirectly influence the environment of life, and through it, its evolution. In these deformative movements, there­ fore, there seems to us to be a universal, simultaneous, and fundamental basis for the sub-division of the earth’s history. It is all the more effective and applicable, because it controls the progress of life, which furnishes the most available criteria for its application in detail to the varied rock forma­ tions in all quarters of the globe. “ The main outstanding question relative to this classification is whether the great deformative movements are periodic rather than continuous, and co-operative rather than compensatory. This can only be settled by com­ prehensive investigation the world over; but the rapidly accumulating evidence of great base-levelling periods, which require essential freedom from serious body deformation as a necessary condition, has a trenchant bearing on the question. So do the more familiar evidences of great sea transgressions, which may best be interpreted as consequence of general base-levelling and concurrent sea-filling, abetted by continental creep dur­ ing a long stage of body quiescence. It is too early to affirm, dogmatically, the dominance in the history of the earth of great deformative movements, separated by long intervals of essential quiet, attended by (1) base-levelling, (2) sea-filling, (3) continental creep, and (4) sea-transgression; but it re­ quires little prophetic vision to see a probable demonstration of it in the near future. Subordinate to these grander features of historical progress, there are innumerable minor ones, some of which appear to be rhythmical and systematic, and some irregular and irreducible to order. These give rise to the local epochs and episodes of earth-history, for which strict intercontinental correlation cannot be hoped, and which must be neglected in the general history as but the individualities of the various provinces. “ The periods which have been recognized in the Palaeozoic and Meso­ zoic, chiefly on the basis of European and American phenomena, seem to us likely to stand for the whole world, with such emendations as shall come with widening knowledge.” J Trias of Spiti The Triassic system of Spiti—Triassic rocks are developed along the whole nothern boundary of the Himalayas, constituting the great scarps of the plateau of Tibet, but nowhere on such a scale of perfec­ tion as in Spiti and the adjoining provinces of Garhwal and Kumaon. (See Figs. 11, 19 and 21.) A perfect section of these rocks, showing

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the relations of the Trias to the system below and above it, is exposed j at Lilang in Spiti. From this circumstance the term Lilang system is used as a synonym for the Triassic system of Spiti. The component members of the system are principally darkcoloured limestones and dolomites, with intercalations of bluecoloured shales. The colour, texture, as well as the whole aspect of the limestone, remain uniform over enormous distances without show­ ing local variations. This is a proof of their origin in the clear deep waters of the sea free from all terrigenous sediments. The rocks are richly fossiliferous at all horizons, a circumstance whicE permits of the detailed classification of the system into stages and zones. The primary division of the Himalayan Trias is into three series, of very unequal dimensions, which, so far as they denote intervals of time, are the homotaxial equivalents of the Bunter, Muschelkalk and Keuper series of the European (Alpine) Trias. The following section from Dr. Hayden’s Memoir gives a clear idea of the classification of the system : 1 Jurassic : (Rhaetic ?) Massive Megalodon limestone.

Keuper 2800 ft.

Muschelkalk, 400 ft.

Bunter, 50 ft.

P erm ia n :

(Quartzites with shales and limestones: Lima, Spirigera. “ Monotis shale ” : sandy and shaly limestone. Coral limestone. Juvavites beds : sandstones, shales and limestones. " Tropites beds : dolomitic limestone and shales. Grey shales: shaly limestone and shales with Spiriferina, Rhynchonella, Trachyceras, etc. Halobia beds : hard dark limestone with Halobia, Arcestes, etc. f Daonella limestone: thin black limestone with shales, Daonella, Ptychites. - Limestone with concretions. Grey limestone with Ceratites, Sibirites, etc. Nodular limestone (Niti limestone). ' Nodular limestone. Limestone and shale with Aviculopeden. Hedenstroemia zone. - MeeJcoceras zone, M. varahaa. Ophiceras zone, 0. sakuntala. kOtoceras zone, 0. woodwardi. Productus shales.

Geology of Spiti, Mem. O .S.I. vol. xxxvi. pt. 1, p. 90.

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Tnassic fauna—The Lower Trias is thin in comparison with the other two divisions of the system, and rests conformably on the top of the Productus shales. The rocks are composed of dark-coloured shales and limestone, with an abundant ammonite fauna. Besides .those mentioned in the section above, the following genera are imiportant: Tirolites, Ceratites, Danubites, Flemingites, Stephanites, with Pseudomonotis, Rhynchonella, Spiriferina and Retzia. The middle division is thicker, and largely made up of concre­ tionary limestones. This division is also widespread and capable of detailed subdivision into stages and zones, which preserve a uniform Daonella [fmestone

Daonella shales

Meekoceras zone Ophiceras zone Otoceras zone

• F ig . 21.—Section of tho Trias of Spiti. 1. Productus shales (Permian). 3. Muschelkalk. 2. Lower Trias. 4. Upper Trias (lower part only). Hayden, Mem, G.S.I., vol. xxxvi. pi. i.

character, both faunistic and lithological, over Spiti, Painkhanda, Byans, and Johar. This division possesses a great palaeontological interest because of the rich Muschelkalk fauna it contains, resembling in many respects the Muschelkalk of the Alps. The Upper Muschel­ kalk is especially noted for the number and variety of its cephalopod fossils ; it forms indeed the richest and most widely spread fossil horizon in the central and N.W. Himalaya, The most typical fossil

171

belongs to the genus Ceratites ; besides it there are : (Ammonites) Ptychites, Trachyceras, Xenaspis, Monophyllites, Gymnites, Sturia, Proarcestes, Isculites, Hollandites, Dalmanites, Haydenites, Pinacoceras, Buddhaites with Nautilus {sp. spitiensis), Pleuronautilus, Syringonautilus and Orthoeeras. The brachiopods are Spiriferina and Spirigera ; Daonella and Halobia are the leading bivalves. The uppermost division of the Trias is by far the thickest, and is composed of two well-marked divisions—dark shales and marl beds at the lower part, and of thick grey-coloured limestone and dolomite in the upper, with an abundant cephalopodan fauna, whose distribu­ tion often characterises well-marked zones. The lower of the two divisions corresponds to the Carnic and Noric stages of the Alpine Trias, while the uniform mass of limestones overlying it probably represents the Rhaetic of the Alps (cf. Kioto limestone, p. 178). The faunistic resemblance between the Triassic rocks of the Himalayas and Alps suggests open sea communication maintained by the Tethys between these two areas since the beginning of the Per­ mian. This sea provided a free channel of migration and intercom­ munication between the marine inhabitants of the central zone of the earth from the Mediterranean shores of France to the eastern borders of China, and maintained this waterway up to the beginning of the Eocene period. The commonest fossils are again : (Ammonites) Joannites, Halorites, Trachyceras, Tropites, Juvavites, Sagenites, Sirinites, Hungarites, Gymnites Ptychites, Griesbachites. Lamelli­ branchs are also numerous, the most commonly occurring forms are Lima, Daonella, Halobia, Megalodon, Monotis, Pecten, Avicula, Corbis, Modiola, Mytilus, Homomya, Pleuromya, with the addition of the aberrant genera Radiolites and Sphaerulites of the Rudistae family of the lamellibranchs. The brachiopods are very few, both as regards number and their generic distribution, being confined to Spirigera, Spiriferina, Rhynchonella, and their allied forms. The Triassic fauna shows a marked advance on the fauna of the Productus limestone. The most predominant element of the former is cephalopods, while that of the latter was brachiopods. This is the most noteworthy difference, and signalises the extinction of large numbers of brachiopod families during the interval. This class of the Molluscoidea entered on their decline after the end of the Palaeozoic era, a decline which has steadily persisted up to the present. During the Mesozoic era the brachiopods were represented by three or four genera like Terebratula, Rhynchonella, Spirigerina. etc. The place of the brachiopods is taken by the lamellibranchs, which have greatly

F ig . 23.___________________________________________________________________________________________________________________

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T H E TRIASSIC SYSTEM

increased in genera and species. The cephalopods, the most highly organised members of the Invertebrata, will henceforth occupy a place of leading importance among the fauna of the succeeding Mesozoic systems. Hazara (the Sirban Mountain)

d en u d e d isoclinal folds of the Nummulitic limestones which constitute

F ig . 22.—Diagrammatic section of Mt. Sirban, Hazara. 1. Slate series. 3. Trias. 2. Permo-Carboniferous. 4. Jura, Cretaceous. After Middlemiss, Memoir, Geological Survey of India, vol. xxvi.

one can trace the whole stratigraphic sequence from the base of the Permo-Carboniferous to the Nummulitic limestone. The sections revealed in this hill epitomise in fact the geology of a large part of the North-West Himalaya.1 On the south border of Hazara, in the Kala Chitta hills of Attock district, some strips of Trias limestone are laid bare in a series of 1 Mem. G.S.I, rol. ix. pt. 2, 1872, and Mem. G.S.I. vol. xxvi- 1896.

The Ceratite beds—The Trias is developed, though greatly reduced in its proportion, in the western part of the Salt-Range. The outcrop of the system commences from the neighbourhood of the Chideru hills, and thence continues westward up to a great distance beyond the Indus. I t caps the underlying Pro­ ductus limestone, and accompanies it along a great length of the Range until the disappearance of the latter beyond Kalabagh and Shekh Budin hills. The Triassic development of the Salt-Range comprises only the Lower Trias and a small part of the Middle Trias in actual stratigraphic range, but these horizons are com­ pletely developed, and they include all the cephalopod-zones worked out in the corresponding divisions of the Spiti section.1 On account of the abundance of the fossil ammonite genus Ceratites the Lower Trias of the Salt-Range is known as the Ceratite beds. The rocks compris­ ing them are about a hundred feet of thin flaggy limestone, which overlie the Chideru stage quite con­ formably, from which also they are undistinguishable lithologically.

Overlying beds are grey limestones and marls, nodular at places. Besides Ceratites, which are the leading fossils, the other ammonites are Ptychites, Gyronites, Flemingites, KonincJcites, Prionolobus, etc. Fossil

3. Trias. 4. Jura and Cretaceous. Section showing the Hazara Mesozoic.

' The Trias of the Salt-Range

1. Slate series.

The Trias is found in Hazara occupying a fairly large area in the south and south-east districts of this province, resting on. the pre­ sumed Permo-Carboniferous series of sediments underlain by a glacial conglomerate, which was previously referred to as the Infra-Trias. The Triassic system of Hazara consists, at the base, of about 100 feet of felsitic or devitrified acid lavas of rhyolitic composition, succeeded by a thick formation of rather poorly fossiliferous limestone, in which the characteristic Upper Triassic fossils of the other Himalayan areas are present. The Lower and Middle Trias are absent from Hazara. The limestone is thickly bedded, of a grey colour, sometimes with an oolitic structure. Its thickness varies from 500 to 1200 feet. These rocks form the base of a very complete Mesozoic sequence in Hazara, which though considerably thinner, is similar in most respects to that of the geosynclinal zone of the Northern Himalayas, so typically dis­ played in the sections in the Spiti Valley and in Hundes. Mt. Sirban—A locality famous for geological sections in Hazara is Mt. Sirban, a lofty hill lying to the south of Abbotabad. Most of the formations of Hazara are exposed with wonderful clearness of detail, in a number of sections along its sides (see Figs. 22 and 23), in which

these liill-masses.

5. Eocene.

GEOLOGY OF IN D IA

172

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shells are found in large numbers in the marly strata, of which the common genera are Cardinia, Gervillia, Rhynchonella and Terebratula. A very curious fossil in the Ceratite beds is a Belleroplion of the genus Stachella, the last survivor of the well-known Palaeozoic gastropod. The Ceratite beds are succeeded by about 100 to 200 feet of Middle Trias (Muschelkalk), composed of sandstones, crinoidal limestone and dolomites full of cephalopods, whose distribution char­ acterises zones corresponding to the lower portion of the Middle Trias of Spiti and Kashmir. Some of the clearest sections of these and younger Mesozoic formations are to be seen in the gullies and nullahs of the Chideru hills of the range. There is a deep ravine near Musa Khel, the Nammal gorge, which has dissccted the whole breadth of the

several thousand feet of shales and slates, with a few intercalations of limestone. They contain the Upper Trias species of Monotis and a few ammonites like Didymites, Halorites, Rhacophyllites. The Trias of Baluchistan rests unconformably on an older Productusbearing limestone, enclosing a foraminiferal limestone, Fusulina lime­ stone, of Permo-Carboniferous age.

F ig . 24.—Section through the Bakh Ravine from Musa Khel to Nammal.

About natural scale, 3 inches = 1 mile. Wynne, Salt-Range, Memoir, G.S.I. vol. xiv.

mountain from Nammal to Musa Khel, and the section laid bare in its precipices comprehends the stratified record from the Permian to the Pliocene, with but few interruptions or gaps. As one walks along the section to the head of the gorge, one passes in review the rock-records of every succeeding age from the Productus limestone, through the representatives of the Trias, Juras, Eocene and Miocene, with at the very top the Upper Siwalik boulder-conglomeratcs. After the Middle Trias there comes a gap in the continuance of the Salt-Range deposits, indicating a temporary withdrawal of the sea from this area. This cessation of marine conditions has produced a blank in its geological history covering the Upper Trias and the early part of the Jurassic period.

175

Burma A very similar development of the Triassic system, also restricted to the uppermost (Rhaetic or Noric) horizon, occurs in the Arakan Yoma of Burma. The fossils are a few ammonites and lamellibrancli3 , of which Halobia and Monotis are the most common. The only known occurrence of Lower Triassic rocks and fossils in Burma was recorded by M. R. Sahni at Na-hkam in the Northern Shan States. Among the genera represented are Ophiceras, Juvenites, Hemiprionites, Naticopsis, Platyceras, Lingula, etc. The fauna is of shallow water facies, ammonites forming the dom­ inant element, while the calcareous brachiopods are entirely absent. It therefore presents a striking contrast to the Burmese anthracolithic faunas in wrhich calcareous brachiopods predominate and ammonites are absent. With the exception of a few fragments of Upper Trias ammonites from the Burmo-Siamese frontier and a Turonian species from Ramri Island, the Na-hkam fauna contains the only am­ monites so far known from Burma. Napeng series—Also, what are known as the Napeng beds occur in a number of scattered small outcrops in the Northern Shan States. (See Fig. 20, p. 164.) The beds are composed of highly argillaceous, yellow-coloured shales and marls, with a few nodular limestone strata. The fossils are Avicula contorta, Myophoria, Gervillia praecursor, Pecten, Modiolopsis, Conocardium, etc. Although some of these are survivals of Palaeozoic genera, the other fossils leave no doubt of the Triassic age of the strata, while the specific relations of the latter genera suggest a Rhaetic age.1

Baluchistan In the Quetta and Zhob districts of North Baluchistan outcrops of Triassic rocks appear as inliers in the anticlines of the more widespread Lias development, which are marked by the exclusive prevalence of the uppermost Triassic or Rhaetic stage, no strata referable to the Lower and Middle Trias being found in this province. The rocks are

Kashmir As is generally the case with the other rock systems, the develop­ ment of the Trias in Kashmir is on much the same scale as in Spiti, if indeed not on a larger scale. A thick series of compact blue limestone, 1 Mem. G.S.I. vol. xxxix. pt. 2, 1913.

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slates and dolomites is conspicuously displayed in many of the hills bordering the valley to the north, while they have entered largely into the structure of the higher parts of the Sind, Lidar, Gurais and Tilel valleys and of the north-east flanks of the Pir Panjal (p. 420). CHAPTER X III

R EFE R E N C E S K arl Diener, Trias o f the Him alayas, Mem. G .S.I. vol. xxxvi. pt. 3, 1912, and Triassic Fauna o f th e H imalayas, Pal. Indica, Series XV. vol. ii. pts. 1 and 2 (1897). E. Mojsisovics, Cephalopoda o f the U pper Trias, Pal. Indica, Series XV. vol. iii, pt. 1 (1899). W. W aagen, Fossils of th e Ceratite Beds, Pal. Indica, Series X III. vol. ii. (1895).

T H E JURASSIC SYSTEM

Instances of Jurassic development in India—In the geosynclinal zone of the Northern Himalayas, Jurassic strata conformably overlie the Triassic in a great thickness of limestone and shales. The succession is quite normal and transitional, the junction-plane between the two systems of deposits being not clearly determinable in the type section at Lilang. Marine Jurassic strata are also found in the Salt-Range, representing the middle and upper divisions of the system (Oolite). The system is developed on a much more extensive scale in Baluchi­ stan, both as regards its vertical range and its geographical extent. A temporary invasion of the sea (marine transgression), over a large part of Rajputana, in the latter part of the Jura gave rise to a thick series of shallow-water deposits in Rajputana and in Cutch. A fifth instance of Jurassic development in India is also the result of a marine transgression on the east coasts of the Peninsula, where an oscillation between marine and terrestrial conditions has given rise to the inter­ esting development of marine Upper Jurassic strata intercalated with the Upper Gondwana formation. Life during the Jurassic—Cephalopods, especially the ammonites, were the dominant members of the life of the Jurassic in all the above­ noted areas. Although perhaps they reached the climax of their de­ velopment at the end of the Trias in the Himalayan province, they yet occupied a place of prominent importance among the marine forms of life of this period, and are represented by many large and diversified forms with highly complex-sutured shells. Nearly 1000 species and over 150 genera have been found in the Jurassic rocks of Cutch ; the majority of the species are new and restricted to the West Indian province. Lamellibranchs were also very numerous in the Jurassic seas, and held an important position among the invertebrate fauna of the period. A rich Jurassic flora of cycads and conifers peopled the land regions of India. The lower classes of phanerogams had already appeared and taken the place of the seed-fern (pteridosperm) and the horsetail of the Permo-Carboniferous periods. w.a.i.

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The land was also inhabited by a varied population of fish, amphibia and several orders of reptiles, besides the terrestrial invertebrates. We have already dealt with the relics of the latter class of organisms in the description of the Gondwana system.

lower part of the Kioto limestone is also sometimes designated as the Para stage, while the part above the Megalodon limestone is known as the Tagling stage. Spiti shales—The Kioto limestone is overlain conformably by the most characteristic Jurassic formation of the inner Himalayas, known as the Spiti shales. (See Fig. 25.) These are a group of splintery black, almost sooty, micaceous shales, about 300 to 500 feet thick, contain­ ing numerous calcareous concretions, many of which enclose a wellpreserved ammonite shell or some other fossil as its nucleus (Saligram). The shales enclose pyritous nodules and ferruginous partings and, to­ wards the top, impure limestone intercalations.- The whole group is very soft and friable, and has received a great amount of crushing and compression. These black or grey shales show a singular lithological persistence from one end of the Himalayas to the other, and can be traced without any variation in composition from Hazara on the west and the northern confines of the Karakoram range to as far as Sikkim on the east. These Upper Jurassic shales, therefore, are a valuable stratigraphic unit, or “ reference horizon ” , in the geology of the Himalayas, of great help in unravelling a confused or compli­ cated mass of strata, so usual in mountainous regions where the natural order of superposition is obscured by repeated folding and faulting. Fauna of the Spiti shales—The Spiti shales are famous for their great faunal wealth, which has made great contributions to the Jurassic geology of the world. The ammonites are the preponderant forms of life preserved in the shales. The enumeration of the follow­ ing genera gives but an imperfect idea of the great diversity of cephalopodan life : Phylloceras, Lytoceras, Hoploceras, Hecticoceras, Oppelia, Aspidoceras, Holcostephanus (Spiticeras), the most common fossil, Hoplites, Perisphinctes and Macrocephalites. Belemnites are very numerous in individuals, but they belong to only two genera, Belemnites (B. gerardi) and Belemnopsis. The principal lamellibranch genera are : Avicula (A. spitiensis), Pseudomonotis, Aucella, Inoceramus gracilis, Lima, Pecten, Ostrea, Nucula, Leda, Area (Cucullaea), Trigonia, Astarte, Pleuromya, Cosmomya, Homomya, Pholadomya; gastropod species belong to Pleurotomaria and Cerithium. The fauna of the Spiti shales indicates an uppermost Jurassic age—Portlandian and Argovian. They pass conformably into the overlying Cretaceous sandstone of Neocomian horizon (Giumal sandstone). Upper Jurassic deposits of Spiti shales facies cover large areas of

178

y

JURASSIC OF THE CENTRAL HIMALAYAS Spiti

Kioto limestone—In the Zanskar range of Spiti, Garhwal and Kumaon, as far as the west frontier of Nepal, the Upper Trias (Noric stage) is succeeded by a series of limestones and dolomites of great thickness, the lower part of which recalls the Rhaetic of the Alps, while

F ig .

25.—Section of the Jurassic and Cretaceous rocks of Hundes. 4. Cretaceous fiysch. 2. Spiti shales. 5. Basic igneous rocks. 3. Giumal sandstone. After Von Krafft, Mem.. G.S.I. xxxii. pt. 3. 1. Kioto limestone.

the upper is the equal of the Lias and part of the Oolite. The bottom beds of the series, containing shells of Megalodon, pass up into a mas­ sive limestone, some 2000 to 3000 feet thick, called the Great lime­ stone, from its forming lofty precipitous cliffs facing the Punjab Himalayas. They are better known under the name of the Kioto limestone. The lithological characters of this limestone indicate the existence of a constant depth of clear water of the sea during its formation. The passage of time represented by this limestone is from Rhaetic to Middle Oolite, as evidenced by the changes in its fauna. The highest beds of the Kioto limestone are fossiliferous, containing a rich assemblage of belemnites and lamellibranchs, and are known as the Sulcacutus beds from the preponderance of the species Belem­ nites sulcacutus. The greater part of the Kioto limestone—the middle —is unfossiliferous. A fossiliferous horizon—the Megalodon lime­ stone—occurs again at the base, containing numerous fossil shells of Megalodon and Dicerocardium. Other fossils are Spirigera, Lima, Ammonites, Belemnites, with gastropods of Triassic affinities. This

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central and southern Tibet, according to the accounts of Sven Hedin, overlain by an enormous spread of the Cretaceous. The Jurassic is folded into long isoclinal belts, carrying outlier strips of the Cretaceous and Eocene. The following table shows in a generalised manner the Jurassic succession of the Central Himalaya : Giumal sandstone. Spiti shales

(500 ft.). Kioto limestone

(3000 ft.).

[Lochambel beds. "J Chidamu beds. [Belemnites beds. ?Sulcacutus beds. I Great thickness of massive limestones, 1 unfossiliferous (Tagling stage). I Megalodon limestone (Para stage). Monotis shale.

Neocomian (Wealden). Portlandian. Callovian. Lias (Rhaetic in part). Noric.

Eastern Himalayas—Mt. Everest Region Vast tracts of the Himalayas east of the Ganges—the Nepal and Assam Himalayas—are yet geologically unknown, but the successive Mt. Everest Expeditions have elucidated the geology of the neigh­ bouring tracts north of Darjeeling and Sikkim. Hayden, Heron, Odell, and Wager have geologically surveyed large areas of Sikkim and Southern Tibet. Immediately to the north of the crystalline axis of the high range culminating in the peak of Mt. Everest there lies a broad expansive zone of much folded and disturbed Jurassic strata, composed of monotonous black shales and argillaceous sandstones, probably the easterly representatives of the Spiti shales. The Jurassic shales are unfossiliferous for the most part, but a few obscure ammonites, belemnites and crinoids have been obtained from them. In the tightly compressed and inverted folds of the Jurassic rocks are outliers of Cretaceous and Eocene (Kampa system) rocks, the latter containing Alveolina limestone; while underlying the Jurassic shales, and adpressed against the crystalline rocks at the foot of Mt. Everest on its north slopes, is a thick series of metamorphosed fossiliferous lime­ stones, quartzites and shales (Lachi series) which has yielded some well-preserved brachiopods, Productus and Spirifer, of probably Permo-Carboniferous affinities. Immediately underlying theee is a

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dark grey limestone, about 1000 feet thick, followed by a yellow, slabby, schistose limestone, which together build the actual summit of Mt. Everest—the Mt. Everest limestone series. Their age is believed to be Upper Carboniferous or somewhat newer. The thick zone of rocks which come below the Mt. Everest limestone, consists of meta­ morphosed foliated slates p,nd schists referable to the Daling series. This zone is extensively injected by granite of Tertiary age. The prevalent tectonic strike of the mountains here is due east to west, the regional dip being to the north. To the east of the river Arun the strike undergoes a sharp bend to the south. South of the Everest-Kanchenjunga group, to as far as the Dar­ jeeling Duars, the geology is more complicated, the rocks being a complex of crystalline metamorphic schists, gneisses, and Tertiary injection-granites, with here and there patches of the Dalings. The latter series ends abruptly to the south of Kurseong, by a mechanical thrust contact in a narrow belt of coal-bearing Gondwana rocks of Damuda age. These in turn are inverted and thrust over the Upper Tertiary Siwalik belt of the foot-hills, the structural relations being here similar to those observed all along the south foot of the Himalayas west of the Ganges. Tal series—In the Lesser Himalayas east of the Ganges, in the zone lying between the outer Tertiary zone and the inner crystalline zone of the main snow-covered range, and distinguished by the exclusive occurrence in it of highly metamorphosed old (Purana) sediments only, there is noted an exceptional development of patches of fossili­ ferous Jurassic (?) beds underlying the Eocene Nummuiitic limestone. This is one of the rare instances of fossiliferous pre-Tertiary rocks \ being met with south of the central axis of the Himalayas, and is therefore interesting as indicating a slight trespass of the shores of the Tethys beyond its usual south border (see p. 149). The fossils ar^few and undeterminable specifically ; they are fragments of belemnites, corals and gastropods. These beds, known as the Tal series, overlie | with a great unconformity older limestones belonging to the Deoban { or Krol series of indeterminate Palaeozoic age. Lithologically the Tal series consists of sandstones and black shales^ with fossil plant-impressions in the lower part of the series and! arenaceous blue limestones containing comminuted shells in the! upper. Tlie principal outcrops of the series are in the Tal tributary of the Ganges, covering large areas in western Garhwal. The fossils are not very helpful in indicating the exact age of the rocks, but they approximately indicate Jurassic affinities.

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Baluchistan

Hazara

Jurassic of Baluchistan—Marine Jurassic rocks, of the gcosynclinal facies, and corresponding homotaxially to the Lias and Oolite of Europe, are developed on a vast scale in Baluchistan, and play a prominent part in its geology. The liassic beds are composed of massive blue or black, crinoidal, oolitic or flaggy limestone, interbedded with richly fossiliferous shales, attaining a thickness of more than 3000 feet, in which the principal stages of the European Lias can be recognised by means of the cephalopods and other molluscs entombed in them. The Liassic limestones are overlain by an equally thick series of massive grey, thick-bedded limestone of Oolitic age, which is seen in the mountains near Quetta and the ranges running to the south. The top beds of the last-described limestone contain numerous ammonites, among which the genus Macrocephalites, represented by gigantic specimens of the species M . polyphemus, attains very large dimensions.

Spiti shales of Hazara—The Jurassic system is developed in Hazara, both in the north and south of the province. The two developments, however, are quite distinct from one another, and exhibit a different facies of deposits. The northern exposure is similar both in its litho­ logical and palaeontological characters to the Jura of Spiti, and con­ forms in general to the geosynclinal facies of the Northern Himalaya. The Spiti shales are conspicuous at the top, containing some of the characteristic fauna. But the Jurassics of south Hazara differ abruptly from the above, both in their composition and their fossils ; they show greater affinity to the Jurassic outcrops of the Salt-Range, which are characterised by a coastal, more arenaceous facies of deposits. The Spiti shales of the Northern zone have yielded these fossils : Oppelia, Perisphinctes, Belemnites, Inoceramus, Cucullaea, Pecten, Gorbula, Gryphaea, Trigonia. To the south of Hazara the Jurassics outcrop in a few inliers in the tightly squeezed isoclinal folds of the Kala Chitta range of hills of the Attock district. The horizons present are the top beds of the Kioto (Lias) limestone, Middle Jurassic and the Argovian (Spiti shales), closely associated with the Giumal series of limestones and sandstones (Albanian or Gault). The fossils present in these rocks are : Velata, Lima, Plicatula, Gryphaea, Chlamys, Mayaites and Perisphinctes.

[The rock-systems of Baluchistan are capable of classification into two broad divisions, comprising two entirely different types of deposits. One of these, the Eastern, is mainly characterised by a calcareous constitution and comprises a varied geological sequence, ranging in age from the PermoCarboniferous upwards. This facies is prominently displayed in the moun­ tain ranges of E. Baluchistan, constituting the Sind frontier. The other facies is almost entirely argillaceous or arenaceous, comprising a great thickness of shallow-water sandstones and shales, chiefly of OligoceneMiocene age. The latter type prevails in the broad upland regions of W. Baluchistan, stretching from the Mekran coast northwards up to the south­ ward confines of the Helmand desert. These differences of geological structure and composition in the two divisions of Baluchistan have deter­ mined in a great measure its principal physical features.] 1 All the Mesozoic systems are well represented in East Baluchistan, and are very prominently displayed in the high ground extending meridionally from the Takht-i-Suleman mountain to the Mekran coast. In the broad arm or gulf of the Tethys which, as we have already stated, occupied Baluchistan, almost since the commence­ ment of its existence, a series of deposits was formed, representative of the ages th at followed this occupation. Hence the main Mesozoic formations of the Northern Himalayas find their parallels in Baluchi­ stan along a tract of country folded in a series of parallel anticlines and synclines of the Jura type, stretching in a north to south direction.2 1 E. W. Vredenburg: Rec. G.S.I. vol. xxxviii. pt. 3, 1910. 2 See Vredenburg’s Map of Baluchistan, Rec. G.S.I. vol. xxxviii. pt. 3, 1910, and

Pal. Ind. New Series, vol. iii. mem. 1, 1909—Introduction.

183

Burma Namyau beds—Jurassic strata are met with in the Northern Shan States, and are referred to as the Namyau beds, also sometimes de­ signated the Hsipau series. (See Fig. 12, p. 117.) The rocks are red or purple sandstones and shales, unfossiliferous in the main, but the few limestone bands have yielded a rich brachiopod fauna with some lamellibranchs of Upper Jurassic age. There are no ammonites present. This group of strata is underlain by shales and concretionary limestones, which have already been referred to as the equivalents of the Rhaetic or Napeng series of Burma. Rocks belonging to the Lias horizon occur at Loi-an, near Kalaw, in the Southern Shan States, enclosing a few coalmeasures, the plant-bearing beds of which have yielded, among fossil conifers and cycads, the characteristic species GinJcgoites digitata. The Loi-an coal-measures support a small coal-field.

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Salt-Range Jurassic of the Salt-Range—The middle and upper divisions of the Jurassic are represented in the Salt-Range. To the east of about longitude 72° the Jurassic is missing owing to the pre-Tertiary denuda­ tion, which was progressively more pronounced from west to east in the Salt-Range. In the north-western part of the Salt-Range, near Nammal and Khairabad, the Jurassic beds thicken to at least 1200 feet and form prominent strike ridges. Still further west in the transIndus Salt-Range the gap in the sequence below the Tertiary becomes much less marked and the Jurassic system attains a thickness of 1500 feet. The Surghar range, north-west of Isa Khel, is composed almost wholly of Jurassic and Eocene (Nummulitic) rocks. The Jurassic strata of the trans-Indus ranges may be summarised in the following table : White sandstones with dark shales, 60 ft. Neocomian fossils. ' Upper Jurassic—light-coloured, thinbedded highly fossiliferous limestones, and blackish arenaceous shales. Fossils : Pecten, Lima, Ostrea, Homomya, Pholadomya, with several ammonites, belemnites and gastropods. Jurassic strata Middle Jurassic—white and variously tint­ ed soft sandstones and clays with lignite (500-1500 ft.). and coal-partings; pyritous (alum) shales with subordinate bands of lime­ stone and haematite. Fossils : obscure plant remains—Ptilophyllum ; Belemnites, Pleurotomaria, Natica, Mytillus, Ancillaria, Pecten, Myacites, Nerinea, Cerithium, Rhynchonella, etc. Ceratite beds, 370 feet.

Cretaceous.

Mid. and Upper Jurassic.

Triassic.

A section of the above type is seen near Kalabagh on the Indus; a fuller section is visible in the Shekh Budin hills and in the Surghar range. A few coal or lignite seams occur irregularly distributed in the lower part, and are worked near Kalabagh, which yield on an average about 1000 tons of coal per year ; some haematite layers also occur. Fossil plants of Jabalpur affinities, enclosed in these beds, point to the vicinity of land. A few beds of a peculiar oolitic limestone, known as the “ golden oolite ”, are found among these rocks. The rock is a

185

coarse-grained limestone, the grains of which are coated with a thin ferruginous layer. Fossil organisms preserved in these rocks, besides those named in the section above, a re : Ostrea, Exogyra, species of Terebratula, numerous gastropods, many ammonites and belemnites. The spines of numerous large species of echinoids, like Cidaris, and fragments of the tests of irregular echinoids, are frequent in the limestones. A rapidly varying lithological composition of a series of strata, such as that of the Jurassic of the Salt-Range, is suggestive of many minor changes during the course of sedimentation in that a re a ; such, for instance, as changes in the depth of the sea, or of the height of the lands which contri­ bute the sediments, of alterations in the courses of rivers, and of the currents in the sea. [It is in the west and trans-Indus part of the Salt-range that the Meso­ zoic group is developed in some degree of completeness. In the eastern, cis-Indus part, the Mesozoic group is, on the whole, rather incom­ pletely developed and irregularly distributed. The structure of this part of the Salt-Range is one of colossal disturb­ ance, by which the stratigraphy of the mountains is completely obscured. The strata by repeated folding and faulting have acquired such a con­ fused disposition that the natural order of superposition is often sub­ verted, while the faulted and tilted blocks lie against one another in the most intricate disorder imaginable.] Marine Transgressions during the Jurassic period After the emergence of the Peninsula a t the end of the Vindhyan system of deposits, this part of India has generally remained a land

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area, a continental tableland exposed to the denuding agencies. No extensive marine deposits of any subsequent age have been formed on the surface of the Peninsula since that early date. Nature of marine transgressions—In the Jurassic period, however, several parts of the Peninsula, viz. the coasts and the low-lying flat regions in the interior, like Rajputana, were temporarily covered by the seas which invaded the lands. These temporary encroachments of the sea over what was previously dry land are not uncommon in the records of several geological periods, and are caused by th&4_udden decrease in the capacity of the ocean basin by some deformation of the crust, such as the sinking of a large land-mass, or the elevation of a submarine tract. Such invasions of the sea on land, known as “ marine trans­ gressions ”, are of comparatively short duration and invade only low level areas, converting them for the time into epicontinental seas. These temporary epicontinental seas should be distinguished from the geosynclinal or mediterranean seas. The series of deposits which result from these transgressions are clays, sands or limestones of a littoral type, and constitute a well-marked group of deposits, sometimes designated by a special name—the Coastal system. One example of the coastal system we have already seen in con­ nection with the Upper Gondwana deposits of the East Coast. The remaining instances of marine transgressional deposits in the geology of India are the Upper Jurassic of Cutch and Rajputana; / the Upper Cretaceous of Tiichinopoly, of the Narbada valley and of the Assam hills, the Eocene and Oligocene of Gujarat and Kathiawar, and the somewhat newer deposits of a number of places on the Coromandel coast. Deposits which have originated in this manner possess a welldefined set of characters, by which they are distinguishable from the other normal marine shallow-water deposits. (1) Their thickness is moderate compared to the thickness of the ordinary marine deposits, or of the enormous thickness of the geosynclinal formations ; (2) they, as a rule, cover a narrow strip of the coast only, unless low-lands ex­ tend farther inland, admitting the sea to the interior ; (3) the dip of the strata is irregular and sometimes deceptive, owing to currcntbedding and deposition on shelving banks. Generally the. dip is sea­ ward, away from the main land ; consequently the oldest beds are farthest inland while the newest are near the sea. In some cases, however, a great depth of deposition is possible during marine trans­ gressions, as when tracts of the coast, or the continental shelf, undergo sinking, of the nature of trough-faulting, concurrently with deposition.

T H E JU R A SSIC SYSTEM

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Such was the case, for instance, with the basins in which the Jurassics of Cutch were laid down, in which the sinking of the basins admitted of a continuous deposition of thousands of feet of coastal detritus. Such block-faulting is quite in keeping with the horst-like nature of the Indian Peninsula, and belongs to the same system of movements as that which characterised the Gondwana period. Cutch The Jurassics of Cutch—Jurassic rocks occupy a large area of the Cutch State. It is the most important formation of Cutch both in respect of the lateral extent it covers and in thickness. With the exception of a few small patches of ancient crystalline rocks, no older system of deposits is met with in this area. I t is quite probable, how­ ever, that large parts of the country which at the present day are long, dreary wastes of black saline mud and silt (which form the Rann of Cutch) are underlain by a substratum of the Peninsular gneisses to­ gether with the Pur anas. A broad band of Jurassic rocks extends in an east-west direction along the whole length of Cutch, and they also appear farther north in the islands in the Rann of Cutch. Structurally the Jurassic is thrown into three wide anticlinal folds, separated by synclinal depressions, with a longitudinal strike-fault at the foot of the southernmost anticline. The main outcrop attenuates in the middle, owing to the overlap of the younger deposits. The aggregate thick­ ness of the formation is over 6000 feet, a depth quite incompatible with deposits of this nature, but for the explanation given above. The large patch of Jurassic rocks in East Kathiawar around Dhrangadhra belongs to the same formation, and is an outlier of the latter on the eastern continuation of the same strike. The Jurassics of Cutch include four series—Patcham, Chari, Katrol and Umia, in ascending order, ranging in age from Lower Oolite to Wealden. The base of the system is not exposed and the top is unconformably covered either by the basalts of the Deccan Trap formation or by Nummuiitic beds (Eocene). The following table, adapted from Dr. Oldham, gives an idea of the stratigraphic succession : Umia ,, . (oOUU

Marine sandstones with Crioceras, etc., sandstone and shale with cycads, . conifers, and ferns (Gondwana facies). ]yiarine sandstone and conglomerate with V Perisphinctes and Trigonia.

Wealden.

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Sandstone and shale with Perisphinctes and Ophelia. Katrol Ferruginous red and yellow sandstone (1000 ft.). (Kantkote sandstones) with Stephanoceras, Aspidoceras. ^Dhosa oolite, oolite limestone ; Peltoceras, Aspidoceras, Perisphinctes. White limestones; Peltoceras, Oppelia. Chari (1100 ft.). Shales with ferruginous nodules; Peri­ sphinctes, Harpoceras. Shales with “ golden oolite ” ; Macroce„ phalites, Oppelia. Grey limestones and marls with Oppelia, corals, brachiopods, etc. Patcham Yellow sandstones and limestones with (1000 ft.). Trigonia, Corbula, Cucullaea, etc.

T H E JU R A SSIC SYSTEM

Upper Oolite.

Middle Oolite.

Lower Oolite.

Base not seen. Patcham series—The lowest member, Patcham series, occurs in the Patcham island of the Rann, as well as in the main outcrop in Cutch proper. The lower beds are exposed towards the north, and are visible in many of the islands. The strata show a low dip to the south, i.e. seawards. The constituent rocks are yellow-coloured sandstones, and limestones, overlain by limestones and marls. The fossils are prin­ cipally ammonites and lamellibranchs, but not so numerous as in the two upper groups, the leading genera being Trigonia, Lima, Corbula, Gervillaea, Exogyra, and Oppelia, Perisphinctes, Macrocephalites triangularis, Sivajiceras, Stephanoceras ; some species of Nautilus. Chari series—The Chari series takes its name from a village near Bhuj, from where an abundant fauna corresponding with th at of the Callovian stage of the European Jura has been obtained. I t is com­ posed of shales and limestones, with a peculiar red or brown, ferru­ ginous, oolite limestone, known as the Dhosa oolite, at the top. There also occur, at the base, a few bands of what is known as the golden oolite, a limestone composed of rounded calcareous grains coated with iron and set in a matrix. The chief element of the fauna is cephalopods, some hundred species of ammonites being recognisable in them. The principal genera a r e : Perisphinctes, Phylloceras, Oppelia, Macrocephalites (many species), Harpoceras, Peltoceras, Aspidoceras, Reineckia, Mayaites, Choffatia, Indosphinctes, Aptychus, Grossouvria, Stephanoceras. In addition there are three or four species of Belemnites, several of Nautilus, and a large number of lamellibranchs. 3 he Chari group is palaeontologically the most important group of the

189

Jurassic of Cutch, because it has furnished the greatest number of fossil species identical with known European types ; it is divided into the following zones : macrocephalus beds, rehmanni beds, anceps beds, and athleta beds, underlying the Dhosa oolite ; the Dhosa oolite, coming at the top of the Chari series, is the richest in ammonites, being divided into three well-defined zones. The Katrol series—The Chari series is overlain by the Katrol group of shales and sandstones. The shales are the preponderant rocks of this series, forming more than half its thickness. The sandstones are more prevalent towards the top. The shales are variously tinted by iron oxides, which at places prevail to such an extent as to build small concretions of haematite or limonite. The Katrol series forms two long wide bands in the main outcrop in Cutch ; the exposure where broadest is ten miles wide. Besides forms which are common to the whole system the Katrol series has, as its special fossils, Harpoceras, Phylloceras, Lytoceras, and Aptychus. The other Katrol cephalopods a r e : Hibolites, Aspidoceras, Waagenia, Streblites, Pachysphinctes, Katroliceras (many species). The group is divided into lower, middle and upper, capped by the Zamia shales, containing fossil cycads and other plants. A few plants are preserved in the sandstone and shale beds belonging to the Zamia stage, but in such an imperfect state of fossilisation that they cannot be identified and named. The Umia series—Over the Katrol group comes the uppermost divi­ sion of the Cutch Jura, the Umia series, comprising a thickness of 3000 feet of soft and variously coloured sandstones and sandy shales. The lower part of the group is conglomeratic, followed by a series of marine sandstone strata in which the fossils are rare except two species of Trigonia, T. ventricosa and T. smeei, which are, however, very typical. Over this there comes an intervening series of strata of sandstones and shales, which, both in their lithological as well as palaeontological relations, are akin to the Upper Gondwana rocks of the more easterly parts of the Peninsula. The interstratification of these beds with the marine Jurassic should be ascribed to the same circumstances as that which gave rise to the marine intercalations in the Upper Gondwana of the east coast. After this slight interruption the marine conditions once more established themselves, because the higher beds of the Umia series contain many remains of ammonites and belemnites. The Umia group has wide lateral extent in Cutch, its outcrop being much the broadest of all the other series. Its breadth, however, is considerably reduced by the overlapping of a large part of its surface by the Deccan Traps and still younger beds. The fossils yielded by

GEOLOGY OF IN D IA

T H E JU R A SSIC SYSTEM

the Umia series are : species of Williamsonia, Ptilophyllum, Elatocladus, Araucarites, Brachyphy Hum, Cycads and Conifers, which have been enumerated in the chapter relating to the Upper Gondwana. The marine fossils include the genera Crioceras, Acanthoceras, Haploceras, Umiaites, Virgatosphinctes, Aulacosphinctes, Belemnites, with Trigonia smeei and Trigonia ventricosa. The Cutch Jurassic rocks are very rich in fossil cephalopoda. Out of the material lately collected L. F. Spath has distinguished 114 genera, fifty-one of which are new to India, and nearly 600 species, a large percentage of which is of local or provincial type, unknown else­ where. No resemblances are detected with the Mediterranean or with the North-West European province, nor is there seen any affinity with the Boreal province, but there exists a close faunal relationship be­ tween the Jura of Cutch and Madagascar. The rocks above described are traversed by an extensive system of trap dykes and sills and other irregular intrusive masses of large dimen­ sions. In the north they become very complex, surrounding and rami­ fying through the sedimentary beds in an intricate net-work. The intrusions form part of the Deccan Trap series and are its hypogene roots and branches. The Jurassic outcrop of North-East Kathiawar, already referred to, is composed of soft white or ferruginous sandstones and pebble-beds or conglomerates. In this respect, as well as in its containing a few plant fossils, it is regarded to be of Umia horizon. The sandstone is a light-coloured freestone, largely quarried at Dhrangadhra for supply­ ing various parts of Gujarat with a much-needed building material.

with a few badly preserved remains of dicotyledonous wood and leaves. The next group is distinguished as the Jaisalmer limestone, co m p o sed of highly fossiliferous limestones with dark-coloured sand­ stones. The limestones have yielded a number of fossils, among which the more typical are Pholadomya, Corbula, Trigonia costata, Nucula, Pecten, Nautilus and some Ammonites. This stage is regarded as homotaxial in position with the Chari series of Cutch. The Jaisalmer limestone is overlain by a series of rocks which are referred to three distinct stages in succession : Abur beds, Parihar sandstones and Badasar beds. The rocks are red ferruginous sand­ stones, succeeded by a soft felspathic sandstone, which in turn is suc­ ceeded by a group of shales and limestones, some of which are fossili­ ferous. Dr. La Touche, of the Geological Survey of India, has assigned a younger age to the Balmir beds (Cretaceous), mainly from the evid­ ence of the dicotyledonous plant fossils which they contain. Jurassic rocks are also exposed in the southern part of Rajputana, where a series of strata bearing resemblance to the above underlie directly Nummulitic shale beds of Eocene age.

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Rajputana Jurassic of Rajputana—The inroads of the Jurassic sea penetrated much farther than Cutch in a north-east direction, and overspread a great extent of what is now Rajputana. Large areas of Rajputana received the deposits of this sea, only a few patches of which are ex­ posed to-day, from underneath the sands of the Thar desert. I t is quite probable that a large extent of fossiliferous rocks, connecting these isolated inliers, is buried under the desert sands. Fairly large outcrops of Jurassic rocks occur in Jaisalmer and Bikaner. They have received much attention on account of their fossiliferous nature. A number of divisions have been recognised in them, of which the lowest is known as the Balmir sandstone ; it is composed of coarse sediments—grits, sandstones and conglomerates

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R EFE R E N C E S F. Stoliczka, Mem. G .S.I. vol. v. pt. 1, 1865. T. H. D. La Touche, Geology of W. R ajputana, Mem. G .S.I. rol. xxxv. pt. 1, 1902. A. B. W ynne, Geology of the Salt-Range, Mem. G .S.I. vol. xiv. 1878. C. S. Middlemiss, Geology of H azara, Mem. G .S.I. vol. xxvi. 1896. V. Uhlig, etc., F auna of the Spiti Shales, Pal. lndica, Sers. XV. vol. iv. pts. 1, and 2. J . W. Gregory, etc., Jurassic F auna of Cutch, Pal. lndica, Sers. IX . vols. i. to iii. A. B. W ynne, Geology of Cutch, Mem. G .S.I. vol. ix. pt. i. 1872. A. M. Heron, Geology of Mt. Everest, Rec. G .S.I. vol. liv. pt. 2, 1922. L. F. Spath, Revision of the Jurassic Cephalopod Fauna of Cutch, Pal. Ind., N.S., vol. ix., 1927-1933. L. R. Wager in Everest 1933 (Hodder & Stoughton), 1934.

%

T H E CRETACEOUS SYSTEM

CHAPTER XIV T H E CRETACEOUS SYSTEM

Varied facies of the Cretaceous. The geography of India in the Cretac­ eous period—No other geological system shows a more widely diver­ gent facies of deposits in the different areas of India than the Cretac­ eous, and there are few which cover so extensive an area of the country as the present system does in its varied forms. The marine geosynclinal type prevails in the Northern Himalayas and in Baluchi­ stan ; parts of the Coromandel coast bear the records of a great marine transgression during the Cenomanian Age, while right in the heart of the Peninsula there exists a chain of outcrops of marine Cretaceous strata along the valley of the Jsfarbada. An estuarine or fluviatile facies is exhibited in a series of wide distribution in the Central Pro­ vinces and the Deccan. An igneous facies is represented, in both its intrusive and extrusive phases, by the records of a gigantic volcanic outburst in the Peninsula, and by numerous intrusions of granites, gabbros and other plutonic rocks in many parts of the Himalayas, Burma and Baluchistan. This heterogeneous constitution of the Cretaceous is proof of the prevalence of very diversified physical con­ ditions in India at the time of their formation, and the existence of quite a different order of geographical features. The Indian Penin­ sula yet formed an integral part of the great Gondwana continent, which was still a more or less continuous land-mass stretching from Africa to Australia. This mainland divided the seas of the south and east from the great central ocean, the Tethys, which kept its hold over the entire Himalayan region and Tibet, cutting off the northern continents from the southern hemisphere. A deep gulf of this sea occupied the Salt-Range, Western Sind and Baluchistan and overspread Cutch, and at one time it penetrated to the very centre of the Peninsula by a narrow inlet through the present valley of the Narbada. The southern sea at the same time encroached on the Coromandel coast, and extended much further north, over-spreading Assam and probably flooding a part of the Indo-Gangetic depression. It is a noteworthy fact that no communication existed between 192

193

these two seas—of Assam and the Narbada valley—although separated by only a small distance of intervening land. While such was the geography of the rest of India the north-west part of the Peninsula was converted into a great centre of vulcanicity of a type which has no parallel among the volcanic phenomena of the modern world. Hundreds of thousands of square miles of the country between Southern Rajputana and Dharwar, and in breadth almost from coast to coast were inundated by basic lavas which covered, under thousands of feet of basalts, all the previous topography of the country, and converted it into an immense volcanic plateau. We shall consider the Cretaceous system of India in the following order : (i) Cretaceous of the Extra-Peninsula : N. Himalayas—Spiti, Kashmir, Hazara, Chitral. Igneous Action during Cretaceous. Sind and Baluchistan. Assam. Burma. (ii) Cretaceous of the Peninsula : Trichinopoly Cretaceous. Narbada Valley Cretaceous. Lameta series. (iii) Deccan Traps.

CRETACEOUS OF THE EXTRA-PENINSULA Northern Himalayas Spiti: Giumal sandstone—That prominent Upper Jurassic formation, the Spiti shales, of the Northern ranges of the Himalayas constituting the Tibetan zone of Himalayan stratigraphy is overlain at a number of places by yellow-coloured siliceous sandstones and quartzites known as the Giumal sandstone. (See Fig. 25.) In the Spiti area the Giumal series has a thickness of about 300 feet. The deep and clear waters of the Jurassic sea, in which the great thickness of the Kioto limestone was formed, had shallowed perceptibly during the deposition of the Spiti shales. The shallowing became more marked with the deposits of the next group. These changes in the depth of the sea are discern­ ible as much by a change in the characters of the sediments as by changes in the fauna that are preserved in them. The deeper-water

GEOLOGY OF IN D IA

T H E CRETACEOUS SYSTEM

organisms have disappeared from tlie Giumal faunas, except for a few colonies where deep local basins persisted. The fossil organisms en­ tombed in the Giumal sandstone include : (Lamellibranchs) Cardium, Ostrea, Gryphaea, Pecten, Tellina, Pseudomonotis, Area, Opis, Corbis, 1Cucullaea, Tapes ; (Ammonites) Holcostephanus, Hoplites. Chikkim series. Flysch—The Giumal series is succeeded in the area we are considering at present by a group of about 250 feet of white limestones and shales. Fossils are found only in the limestones which underlie the shales. This group is known as the Chikkim series, from a hill of that name in Spiti. The Chikkim series is also one of wide hori­ zontal prevalence, like the Spiti shales, outcrops of it being found in Kashmir, Hazara, Afghanistan and Persia. The fossils that are pre­ served in the limestone are fragments of the guards of Belemnites, shells of the peculiar lamellibranch genus Hippurites (belonging to the family Rudistae) and a number of foraminifers, e.g. Nodosaria, Cristellaria, Textularia, Dentallina, etc., congeners of the foraminifers whose tiny shell-cases have built up the chalk of Europe. In the areas adjacent to Spiti the Chikkim series is overlain by a younger series of west of the point where this change takes place the gypsum is intimately associated with red marl and salt and a little further north­ west at Mari-Indus and Kalabagh the salt is worked on a large scale. Recent work by Gee has demonstrated that the Saline series of this part of the Salt-Range is clearly of Laki age, and riot (as was pre­ viously thought) of Cambrian or pre-Cambrian age. This brings the salt and gypsum into line with a similar group of beds found in the ‘ Kohat district and believed to be of Laki age. [A brief reference has already been made to the Saline series of the central part of the Salt-Range (Khewra, Warcha, etc.). The gypsum, salt, and red marl underlie the Cambrian sequence but the junction is demonstrably an irregular one and there has been much discussion about the relations be­ tween the Cambrian Purple sandstone and the underlying beds (p. 106). It is thought by some geologists that the disturbance is of small extent and is merely an expression of the difference in competence of the beds above and below. This explanation necessitates the assumption that there are two separate Saline series in the same neighbourhood, one of Cambrian and one of Eocene age. This seems an improbability especially in view of the very close similarity of the supposed two sets of beds, and other geologists have interpreted the disturbed junction between the Saline series and the overlying Cambrian rocks as a thrust-fault of major importance which has brought the Cambrian strata on to the Eocene Saline series. So far no de­ finite evidence has been forthcoming to show that the Saline series of the central portion of the Salt-Range is really of Eocene age but the Salt-Range is known to include a series of important over-thrust faults and it does not seem improbable that there is a thrust-plane running along the base of the range. Further evidence of movement between the Saline series and the overlying beds is provided by the sections near Musa Khel; here the red marl and gypsum are overlain not by Cambrian beds but by the Talchir

T H E EO C EN E SYSTEM

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boulder-bed and at many places along the junction the-boulders have been greatly sheared. Near Khewra, the accumulation of gypsum and rock-salt is on a large scale. At the Mayo Salt Mines, at Khewra, there is a mass of nearly pure crystalline salt of a light pink colour, interbedded with some seams of im­ pure red earthy salt (Kalar), of the total thickness of 300 feet. Above this is another bed of the thickness of 250 feet. The upper deposit is not so pure as the lower, for it contains more intercalations of Kalar and is associated with other salts, viz. calcium sulphate, and magnesium, potassium, and calcium chlorides in greater proportions. The lateral extension of the saltbeds appears to be very great, amounting to several square miles in area and there is thus a very large supply of salt from the Khewra deposits. To this must be added the salt contained in the red marl at other parts of the range, and worked in several smaller mines. The associated gypsum occurs in large masses and also in smaller beds; it exhibits an irregular bedding and varies greatly in purity and in degree of hydration, passing at times into anhydrite. /T h e origin of the salt-marl is not known with certainty. Oldham sug­ gested that it is an alteration product of pre-existing sediments by the| action of acid vapours and solutions. Christie has brought forward evi­ dence to show that the salt and gypsum were formed by the evaporation of i sea-water in inland or enclosed basins which were intermittently cut off from the main ocean by barriers. The red saline earth or Kalar-seams are held to indicate the last stage of the desiccation of the sea-bed ; the occur­ rence of potassium-salts mentioned below, just underneath the Kalar, is pointed to as further evidence in support of the evaporation theory ; for, in a sea-basin undergoing desiccation, the salts of potassium are the last to be precipitated, after nearly 98 per cent, of the water has evaporated. It is argued that the stratification-planes which were originally present, both in the enclosing marl and in the salt, have been obliterated subsequently by superficial agencies as well as by the effects of compression and earthmovements on a soft plastic substance like the marl. In 1920 Pascoe adduced evidence to prove that the apparent infraCambrian position of the salt-marl is not its normal stratigraphic position, but that the salt and gypsum, both of which he believes to be of sedimentary origin, are of Eocene age, their present position being brought about by an overthrust. There is no doubt that although much of the Saline series outcrop is de­ void of clear stratification, other parts show the clearest disposition of the different components of the Saline series into distinct beds which are of sedimentary origin. This is particularly shown by the dolomites and shales associated with the red marl, and also by the bands of gypsum and salt. This prominent stratification shows that hypotheses based on an “ igneous ” or “ intrusive ” origin are inapplicable, and that the Saline series is in the main of sedimentary origin. Nevertheless, the discovery in Kohat and in the north-west end of the Salt-Range shows that the gypsum is—at least in part—an alteration product of limestones. The intimate association of limestones and shales with the gypsum in the Salt-Range is closely par­ alleled in Kohat.

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Economics—The economic importance of the salt deposits is great, as they produce about 150,000 tons of salt per year. Besides the chloride of sodium, there are found other salts, of use in agriculture and industries. Of the latter the salts of Potassium (Sylvite, Kainite, Blodite and Langbeinite), which occur in seams underlying beds of red earthy salts (Kalar), are the most important. Magnesium salts are Epsomite, Kieserite and Glauberite.] Kohat The Rock-salt deposits of Kohat—A short distance to the north-west of the Salt-Range a t Bahadur Khel and elsewhere in the hills of the Kohat district, there are outcrops of Kirthar rocks which are remark­ able for being underlain by a great thickness of gypsum and rock-salt. At Bahadur Khel about a thousand feet of these beds are laid bare in a perfect anticlinal section ; the beds of rock-salt, which are seen at the centre of the anticline, are overlain by gypsum, the upper part of which is interbedded with green clay and shale. These beds are in turn succeeded by red clays and by Kirthar limestones containing Nummulites, Alveolina and other fossils. In lateral extent the outcrop of rock-salt is traceable for several miles. The salt is chemically pure crystalline sodium chloride with some admixture of calcium sulphate, but with no associated salts of potassium or magnesium as in the Salt-Range deposits of the same mineral, from which also the Kohat salt differs in its prevailing dark-grey colours and in being slightly bituminous. I t appears quite probable that the two deposits, in spite of these slight differences, have had a common origin, and are of the same age, and th at the apparent infra-Cambrian position of the Salt-Range salt-deposits, as seen near Khewra, is due to overthrust faulting. In the extreme north-west of Kohat the Ranikot beds are strongly developed in the Samana range and have been studied in considerable detail by Col. L. M. Davies. The basal Hangu beds are sandstones and shales with an abundant molluscan fauna ; these constitute the lowest Eocene horizon found in India ; the higher beds are mainly limestones (Lockhart limestones). A more normal facies of the Laki beds (as com­ pared with the Bahadur Khel development) is exposed near Kohat itself. The lowest beds are green clays and shales ; these are overlain by the Shekhan limestone and this by a gypseous red clay. Above this comes the Kirthar series with the Kohat shales, limestones and shales, a t the base followed by the Nummulite shale and Alveolina limestone. The Laki and Kirthar limestones and accompanying shales have been

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traced eastwards and north-eastwards through the Margala and Kala Chitta hills and the Hazara mountains to Muzaffarabad on the Jhelum and thence into Kashmir. Potwar East of Kohat, in the Kala Chitta hills, in the northern part of the Potwar the Eocene beds present a somewhat different facies. There is a strong development of limestones which include both Ranikot and Laki beds, and a thin coaly horizon presumably corresponding to the coal of the Salt-Range. These limestones, which are not strikingly fossiliferous, have been termed Hill Limestone. They are overlain by gypseous limestones which are followed by variegated shales with a few fresh-water fossils. This horizon, known as the Planorbis beds, appears to be the top of the Laki Series, and is associated w^ith seepages of oil. The Kirthar series is represented only by the Kohat shales and the Nummulite shales, the higher beds having been re­ moved during the Oligocene denudation. The range of beds from the Planorbis beds upwards is known as the Chharat series. Hazara Eocene rocks, principally composed of nummulitic limestone, play a prominent part in the geology of Hazara and, indeed, of the whole country around the N.W. frontier. At the base, the coal-bearing Ranikot series is identified, though it does not possess any economic resources, the quantity as well as the quality of coal being very in­ ferior. The nummulitic limestone is a grey or dark-coloured massive rock of great thickness interbedded with nummulitic shale beds and is thus somewhat different from the equivalent beds in the Salt-Range. The limestone passes upwards into the Chharat series of shales and limestones which are unconformably overlain by the Murree series of fluviatile deposits. The Eocene of Hazara extends eastwards beyond the Jhelum into Kashmir, following the great bend of the mountains and, as men­ tioned in the next section, it joins up with the nummulitic border fringing the south-western foot of the Pir Panjal. Kashmir The strong band of nummulitic limestones and associated Kohat, belonging to the Ranikot and Laki series, which stretches from strata through the Hazara mountains to Kashmir, persists as a narrower

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band across the Jhelum, where it turns abruptly round the great syntaxial re-entrant of the mountains and runs along the foot of the Pir Panjal for more than 150 miles. The-width varies greatly, the band widening and narrowing between the two Panjal thrusts (page 310) which bound it on either side. The Eocene is also assoc­ iated with the large inliers of Permo-Carboniferous limestones (page 161) in the younger Tertiaries of the Jammu hills, and includes de­ posits of coal, and aluminium and iron ores. The largest of these inliers are near Riasi and Poonch. Among these the Laki horizon is recog­ nised by the presence of species of Assilina, Alveolina and Nummulites in the nummulitic limestone. A ferruginous pisolite occurs a t the base of the Eocene and is workable as an ore of iron. Also associated with the basal beds at both these localities there occurs an extensive deposit of coal and bauxite and bauxite clays. The occurrence of bauxite near the base of the Eocene, indicating a great regional un­ conformity with the underlying Palaeozoic limestone, is suggestive of a lateritic origin. Outer Himalayas The extent and boundary of the Eocene gulf of North India, re­ ferred to on page 226, can be roughly judged by the extent and dis­ tribution of the outcrops of Nummulitic limestone preserved to-day— a more or less continuous belt extending from Sind and the Sulaiman hills, where it attains maximum development, through Hazara, Muzaffarabad and the Pir Panjal chain, to beyond Dalhousie and Subathu; thence with decreasing width and some intermissions to Naini Tal. The Eocene of the Outer Himalayas of Simla is distinguished as the the Subathu series, which is collateral with part of the Kirthar series, together with its underlying Laki series. The Subathu series is typically developed near Simla, from a military station near which the group takes its name. The rocks are red and grey, gypsiferous and cal­ careous shales, with some interbedded sandstones and subordinate limestones in which Nummulites, and other fossils, are found. This development differs from the more usual Laki and Kirthar beds in the small proportion of limestone. There is also a difference in colour and texture, the Subathu limestone being grey to black in colour, very compact and thinly bedded. The lower beds are very variable and inconstant; there is a workable coal-seam in one locality, but this is missing from the type area, the lower beds being instead ferruginous sandstone and grits containing pisolitic haematite and limonite, .

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Assam The Eocene rocks occupy a large area in Assam, and offer several points of interest. The lowest beds exhibit two sharply contrasted facies, one in the east of the province and the other in the west. In the Naga hills (in the eastern area) the lowest Eocene beds are the Disang shales—a great thickness of very well bedded dark-grey shales with thin well-cemented sandstones. Towards the interior of the hills separating Assam from Burma, the shales become hardened and slaty and are associated with quartz veins and serpentine. I t is just possible th at in this area some of the beds referred to the Disang series are of pre-Tertiary age. In the north-west of Assam, there is developed a calcareous facies of the Eocene ; this occupies a large area in the Shillong plateau (Garo hills, Khasi and Jaintia hills). The lowest beds here have recently been termed by C. S. Fox the Tura stage ; they include sandstones and shales and thin seams of coal. This stage is now believed to include the Cherra sandstone, a band of hard coarse sandstone, and the various outcrops of thin coal occurring in and near the Garo hills ; these were previously thought to be of Cretaceous age. These beds rest with no marked discordance on the Cretaceous but overlap on to the gneiss and other metamorphic rocks. At the base is commonly found kaolin and occasionally laterite. The Tura beds are followed by nummulitic limestones (Sylhet limestone stage) which show considerable lateral variation ; shales and even sandstones are locally developed. The fauna is fairly rich and shows affinities with the Middle Kirthar of North-western India. Above these limestones are the Kopili alter­ nations including shale, thin coal, thin limestone, and thin sandstone; these beds also are fossiliferous. The range of beds including the Tura, Sylhet limestone, and Kopili alternation stages is known as the Jaintia series, corresponding in age to the upper part of the Disang series. Both the Jaintia series and Disang series are overlain by the very thick Barail series which is of considerable economic importance as it contains thick seams of coal. This series includes thick hard sand­ stones which give rise to the Barail range which is the “ backbone ” of Assam ; in addition there is a fairly large proportion of argillaceous beds which increases slightly in a north-eastern direction. The Barail series has been sub-divided into stages on lithological grounds but as fossils are extremely rare it has not been possible to correlate these stages precisely with those in other areas. The Barail beds show an

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important lateral variation ; when traced from south-west to north­ east, the carbonaceous material very steadily increases in amount and the carbonaceous shales pass into coaly shales, shaly coals, and thence into thin coals and so in Upper Assam into thick coals of good quality. In this area, the upper portion of the Barail series forms the coalmeasure sub-series but although the coal seams are fairly numerous, the thick workable seams are restricted to a small portion of the sequence. A few fossils have been found near the coal horizon and these suggest an uppermost Eocene age. I t is therefore probable that the Barail series is partly Upper Eocene and partly Lower Oligocene. Oilshows are found in association with the Barail series in the Surma valley and in Upper Assam. There is no separation of “ oil-measures ” and “ coal-measures ” for, although most of the oilshows are well below the thickest of the coal seams, oilsands often occur in between the thinner coal seams and petroliferous coal seams have been recorded.

soon resumed, however, before the Eocene period came to a close, and in the Yaw stage there is a considerable development of marine beds containing foraminifera.

Burma The Eocene rocks in Burma are developed on a large scale, reaching a thickness of well over 20,000 feet. They show a facies of deposits very different from that of their equivalents in North-west India (Sind, Baluchistan, North-West Frontier Province, the Salt-Range, Kash­ mir, etc.) but have considerable resemblances to the Eocene of Assam. Cotter has divided them into six stages (vide Table on page 238). The Tertiary sequence commences with a basal conglomerate, Paunggyi conglomerate, of Ranikot age, resting over a somewhat obscure group of rocks which form a large part of the Arakan Yoma from Cape Negrais northwards. These are known as the Axial, Mai-i and Negrais groups which probably include beds from Triasic to Cretaceous age. The greater part of the Lower Eocene is made up of the thick Laungshe shales which probably correspond to the Disang shales of Assam and are mainly of Laki age. A few thin seams of coal are met with in the overlying Tabyin clays. The Upper Eocene beds are of great interest. The Pondaung sandstones, about 5,000 feet thick, mark a temporary retreat of the nummuiitic sea which was thrown back by thick deltaic accumulations, in which are preserved the earliest fossil mammals of the Indian region. These belong to the Amynodonts, Metamynodonts and Titanotheres, the ancestral forms of rhinoceroses, and the highly generalised extinct group of ungulates (the Anthracotheres)—Anthracotherium, Anthracohyus, and Anthracokeryx. Marine conditions were

251

R EFE R E N C E S W. T. Blanford, Geology of W. Sind, Mem. G .S.I. vol. xvii. pt. 1, 1879. P. M. D uncan and W. P. Sladen, T ertiary F auna of Sind, Pal. Indica, sers. vii. and xiv. vol. i. pts. 2, 3 and 4, 1882-1884. E. W. Vredenburg, T ertiary System in Sind, Mem. G .S.I. vol. xxxiv. pt. 3, 1906. E. S. Pinfold, Structure and Stratigraphy of N.W . Punjab, Rec. G .S.I. vol. xlix. pt. 3, 1918. E. H. Pascoe, Petroleum Deposits of Punjab and N.W. F rontier Provinces, Mem. G .S.I. vol. xL pt. 3, 1921. W. L. F. N uttall, S tratigraphy of the L aki Series, Q.J.G.S. London, vol. lxxxi. pt. 3, 1925. L M. Davies, R anikot Beds a t Thai, Q.J.G.S. London, vol. lxxxiii. pt. 2, 1927 ; Fossil F auna of the Samana Range, Pal. Indica, N.S. vol. xv., 1930. L. M. Davies and E. S. Pinfold, Eocene Beds of the Punjab Salt-Range, Pal. Indica, N.S. vol. xxiv. mem. 1, 1937. P. Evans, T ertiary Succession in Assam, Trav&. M in. Geol. Inst. Ind. vol. xxvii., ‘ 1932. E. R. Gee, Geology of the Salt-Range, Mem. G .S.I. (under preparation).

T H E OLIGOCENE A N D L O W E R M IOCENE

CHAPTER XIX THE OLIGOCENE AND LOWER MIOCENE SYSTEMS OLIGOCENE Restricted Occurrence—The Oligocene system is very poorly repre­ sented in India and it seems th at during a part of this period a con­ siderable amount of what is now the Tertiary outcrop was undergoing denudation which resulted in the removal of such Oligocene deposits as had been formed, as well as some of the Eocene. The fullest de­ velopments of Oligocene rocks are in Sind and Burma. Rocks which are probably of Oligocene age occur also in Assam. In the few areas in which it is developed, the Oligocene appears to lie conformably upon the Eocene, although it is not impossible that there is a palaeon­ tological break at this horizon. The Oligocene system is usually separated from the overlying Miocene beds by an unconformity or at least a palaeontological break. The Oligocene system appears to be absent from Kohat, the Pun­ jab, Kashmir and the North-WTest Himalaya.

253

The name is derived from the Nari river, along the banks of which a section of the series is seen. The lower part of the Nari is composed of limestone and calcareous rocks, but they give place to finely-bedded sandstones and shales in the upper part. At the top the group con­ sists of coarse deposits, massive sandstones and conglomerates. The shaly partings among the sandstones contain plant impressions, and are thought to be of fluviatile deposition. Among the calcareous bands of the upper part of the Nari, the foraminifers attain their highest development, manifested as much by the organisation of the specific types as by the size attained by the individuals of the species. Large shells or tests of Nummulites of 2 to 3 inches in diameter are not uncommon. The most frequent species are : N. intermedius, N. sublaevigatus, N. vascus, accompanied by Lepidocyclina, and some other foraminifers. Other fossils a re : MontlivdUia, Schizaster, Breynia, Eupatagus, Clypeaster, Lucina, Venus, Area, Corbula, Ostrea (sp. angulata) and Natica, Voluta, etc. The Nari strata are overlain with apparent conformity by the Gaj series which appears to be of Lower Miocene age. Assam Barail Series—It is probable that the uppermost part of the Barail series of Assam is of Oligocene age but the extreme rarity of fossils makes it impossible to establish the age with certainty. The Barail series is overlain with marked unconformity by Lower Miocene rocks. Burma

Baluchistan Flysch—In Baluchistan there is a great thickness of shallow-water sandstones and green arenaceous shales, with only a subordinate lime­ stone ; this closely resembles the Flysch of Switzerland and covers a wTide tract on the Mekran coast. This formation is designated the Kojak shales. Fossils are rare but a few gastropods have been found indicating the Oligocene age of these beds. Sind Nari Series—The Oligocene beds in Sind are more interesting than the almost unfossiliferous Baluchistan Oligocene. They arc known as the Nari series and overlie the Kirthar limestone with apparent con­ formity. 252

Pegu Series—A very fossiliferous development of the Oligocene occurs in Burma and reaches a thickness of as much as 10,000 feet. These beds form the lower half of the Pegu system, the upper half of the system being of Miocene age and separated from the underlying beds by an unconformity. The Lower Pegus have been subdivided into three stages. The lowest, the Shwezetaw sandstones, locally con­ tains a few thin seams of impure coal; when traced from south to north the group shows a passage from marine beds into a continental facies. The Shwezetaw sandstones are overlain by the Padaung clays with a characteristic Middle Oligocene fauna. Above the Padaung clays, there is the Singu stage of Vredenburg including both sand­ stones and shales, but the Burmah Oil Company geologists have put forward a different classification for all the beds above Padaung clays and they have termed the highest Oligocene rocks the Okhmintaung

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the analogy between the three petroleum areas of India—Burma, Assam, and the north-west Punjab, which appear to have been gulfs or arms of the nummulitic sea which were filled up by sedimentation. G. W. Lepper has pointed out that the most prolific fields in Burma are situated on the eastern margin of a broad syncline corresponding approximately to the Chindwin-Irrawaddy valley. He suggests that the bulk of the oil-forming sediments were deposited in a shallow marine environment and that most of the oil of the Burma oilfields has migrated into them from the sediments of this long and broad syncline.

Echinodiscus, Clypeaster, Echinolampas, Temnechinus, Eupatagus, Lepidocyclina and Orbitoides. The species Ostrea latimarginata is highly characteristic of the Gaj horizon, it being met with also in the

256

LOWER MIOCENE Distribution—Unlike the Oligocene, the Miocene system is very fully developed in India, being found in all the Tertiary areas of the extra-Pen: nsula. I t is convenient to deal separately with the Lower Miocene since in several areas this presents a notably different de­ velopment from the upper portions of the system. In Sind the Lower Miocene rocks are known as the Gaj series, in the Potwar and Kashmir as the Murree series. In the Outer Himalayas the term Sirmur was applied to a group ranging from Eocene to Miocene but this term is inconvenient as it does not represent a natural unit, the Oligocene being absent. Consequently the term Sirmur system is now seldom used. The upper part of this group of rocks includes two series— Dagshai and Kasauli which belong to the Lower Miocene. In Assam the Barail series is unconformably overlain by the Surma series which is of Lower Miocene age. In Burma the Upper Pegus are important since they contain a petroliferous horizon, and are very fossiliferous.

c5 U £ O •£ P-i 0 ) O ^^o < D cn ® ■k ° « I

Sind Gaj Series—The Nari strata are overlain with apparent conformity by the Gaj series ; this consists of richly fossiliferous dark-brown coral limestone, with shales, distinguished from the underlying Nari by the absence of Nummulites. The higher beds are red and olive shales which are sometimes gypseous ; these in turn pass up into a series of clays and sandstones whose characters suggest deposition in an estuary or the broad mouth of a river. This shows a regression of the seaborder and its replacement by the wide basin of an estuary. Fossils are very numerous in the marine strata, representing every kind of life inhabiting the sea. The commonly occurring forms are : Ostrea (sp. 0. multicostata and 0. latimarginata), Tellina, Brissus, Breynia,

parallel group of deposits forming the upper part of the Pegu system of Burma. I t is evident from the estuarine passage-beds that the Upper Gaj was the time for the expiry of the marine period in Sind W .Q.I.

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and the beginning of a continental period. On the land which emerged from the sea, a system of continental deposits began to be formed, which culminated in an alluvial formation of great thickness and extent enclosing relics of the terrestrial life of the time. Rhino­ ceros is the only land-mammal whose remains have been hitherto ob­ tained from the Upper Gaj beds. S ilu g ti beds—In the Bugti hills of the Bugti country, in East Baluch­ istan, the fluviatile conditions had established themselves at an earlier date, the marine deposits in that country ceasing with the Nari epoch. The overlying strata, i.e. the lower part of the Gaj, are fluviatile sand­ stones containing a remarkable fauna of vertebrates, of Upper Oligo­ cene or Lower Miocene affinities. The leading fossils are : (Mammals) Anthracotherium, Cadurcotherium, Diceratherium, Baluchitherium (a rhinoceratid, one of the largest land-mammals), Brachyodus, Teleoceras and Telmatodon, together with a few fresh-water molluscs, among which are a number of species of Unio. These beds are known as the Bugti beds.

v ario u s members of the Eocene are overlain by alternating sand­

258

Salt-Range, Potwar, Jammu hills The Potwar trough—One of the most perfect developments and ex­ posures of the whole Tertiary sequence in India is. observed in the geosynclinal trough of the Potwar, a plateau lying between the SaltRange and the foot-hills of the N.W. Punjab. In this area, with the exception of the Oligocene break, continuous sedimentation took place from the Ranikot stage onwards to late Pleistocene, resulting in deposits, 25,000 feet thick, in which fossils belonging to most of the Tertiary time-divisions are recognised. On a floor constituted mainly of Mesozoic rocks there occur about 1000 feet of the Nummulitics, overlain by 6000 feet of the ferruginous, brackish-water sediments of Aquitanian and Burdigalian age, the Murree series, succeeded by over 16,000 feet of the fluviatile and sub-aerial Siwalik strata. At the top, the Upper Siwaliks pass transitionally into the Older and Newer Pleistocene alluvia, loess, gravels, etc. The Potwar trough forms almost the north-western extremity of the much wider and larger Indo-Gangetic synclinorium, also filled up by Tertiary and post-Tertiary deposits, of which the former may be regarded as a small scale replica.1 Murree Series—In the eastern end of the Salt-Range, in the Potwar, und in the hills fringing the Jammu and Kashmir Himalaya, the 1 Memoirs, G.S.I. vol. Ii. pt. 2, 1928; Quart. Jour. Geol. Min. Met. Soc. Ind. vol. iv. No. 3, 193J.

259

stones and shales, the Murree series, very variable in thickness, but exceeding 8000 feet where fully developed. At the base of the series there is often a well-marked conglomeratic bed with bone fragments and derived nummulites. For some time the age of these beds was uncertain. The nummulites are of Eocene age (mainly Kirthar) and the other organic remains of Miocene (Gaj) age. I t was therefore thought that the horizon represented a passage from the Eocene through the Oligocene to the Miocene. When it was recognised that the nummulites were all derived by erosion of the underlying Eocene rocks, the difficulty disappeared and the basal Murrees took their correct place in the succession. This basal zone has been termed the Fatehjang beds. Above the Fatehjang beds comes a great thickness of red and purple shales veined by calcite, with grey and purple, falsebedded, sandstones, and concretionary clay pseudo-conglomerates. The whole thickness is unfossiliferous in the main, but for a few im­ pressions of the leaves of a palm Sabal major and some other obscure leaves and tissues of plants, with rarely some Unionid shells. These beds are known as the Lower Murrees. The Upper Murrees are softer, coarser, and paler sandstones bearing occasional impressions of dicotyledon leaves. They are associated with shales very similar to those of the Lower Murrees but forming a smaller proportion of the succession. The Lower Murrees especially are usually found in narrow isoclinal folds and this, together with their unfossiliferous nature, makes it difficult to work out details of the succession. The range of age presented by the Murree series is difficult to de­ termine, but it is clear th at they are in the main Lower Miocene ; it is not impossible that the lowest beds range down into the Oligocene. There is no sharp upward limit to the series, the passage into the overlying Kamlial stage being quite gradual. The Murree series has a very restricted development in the SaltRange, being absent from the greater part of the area. The gap be­ tween the Eocene and the overlying beds is thus greater than further north. In the western part of the Salt-Range the Eocene is followed by Kamlial beds, but in the trans-Indus area further west successively higher Siwalik horizons rest upon the Eocene. Petroleum—In the Potwar, the Murree series is occasionally associated with petroleum and has yielded a production of about 120 million gallons of oil at Khaur. It is believed that the oil has migrated into the Murree series from the underlying Eocene.

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Outer Himalayas

there is also a strong unconformity between the Pegus and the overlvine Irrawaddy series. Consequently the thickness of the Upper Pegus is very variable. Petroleum is found in the Miocene beds but these are hardly as important a source of this mineral as the Oligo­ cene. The abundant fossils of the Upper Pegus enable the age of the greater part of the group to be definitely identified as Lower Miocene; it is however possible that the uppermost Pegu beds are of Middle Miocene age. The Upper Pegus, like the Lower Pegus, show evidence of passing northwards into rocks deposited in more shallow water conditions. The extent of the unconformity between the Pegus and Irrawaddy varies considerably in different localities and it has been suggested that in some parts of Burma there is very little break be­ tween the two sets of beds.

Dagshai and Kasauli Series—The broad outcrop of the Murree series in the Jammu hills narrows towards the east and merges into the typical Dagshai-Kasauli band of the Simla area, a connection be­ tween the two being discernible in some plant-bearing beds in the valley of the Ravi. The Dagshai beds overlie the Subathus without any marked discordance but there is nevertheless a large break, the whole of the Oligocene being absent. The lower part of the Dagshai series is made up of bright red nodular clay ; the upper is a thickly stratified, fine-grained, hard sandstone which passes up, with a per­ fect transition, into the overlying Kasauli group of sandstones, which rocks are the chief components of the Kasauli series. No fossils are observed in the Dagshai group except fucoid marks and worm-tracks, fossils which are of no use for determining either the age of the deposit or its mode of origin. The Kasauli group also has yielded no fossils except a few isolated plant remains and a Unionid. The only traces of life visible in this thick monotonous pile of grey or dull-green coloured coarse, soft sandstones are some impressions of the leaves of the palm Sabal major. These are of importance because they enable the Kasauli horizon to be recognised further north-west in the Jammu hills. Assam Surma Series—The coal-measures of the Assam hills, belonging to the Barail series described in the last chapter, are unconformably overlain by the Surma series, representative of the Gaj horizon of Sind. The Surma series occupies a wide extent in the Naga hills, North Cachar hills, and Surma valley of Assam, and extends south­ wards through Chittagong to the Arakan coast of Burma. I t is com­ posed of sandstones and sandy shales, mudstones and thin conglo­ merates, generally free from carbonaceous content. In the Garo hills a small range of beds in the Surma series has yielded a large number of marine fossils and another fossiliferous bed has been described from a slightly lower horizon in the Surma valley. Both faunas belong to the Lower Miocene ; otherwise the series is remarkably unfossili­ ferous. Indications of petroleum are common in the Surma series in several localities. Burma Upper Pegu Series—The Upper Pegu rocks of Lower Miocene age form an important part of the Burma Tertiary sequence. As men­ tioned on pages 253-4 there is a break at the top of the Oligocene and

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Igneous action during the Oligocene and Lower Miocene The Middle Tertiary wTas the period for another series of igneous out­ bursts in many parts of extra-Peninsular India. The igneous action was this time mainly of the intrusive or plutonic phase. Unfortunately it is difficult to fix the precise age of these intrusions. The early Eocene rocks were pierced by large intrusive masses of granite, syenite, diorite, gabbro, etc. In the Himalayas, in Baluchistan and in Burma the records of this hypogene action are numerous and of a varied nature. Intrusions of granite took place along the central core of the Himalayas. In Baluchistan the plutonic action took the form of bathyliths of granite, augite-syenite, diorite, porphyrites, etc., while in Upper Burma and in the Arakan Yoma it exhibited itself in peridotitic intrusions piercing through the Eocene and possibly Oli­ gocene strata. In the Myitkyna district of Upper Burma, a basaltic tuff appears to be interbedded with the Tertiary rocks which are mainly of Eocene or Oligocene age. In all the above Tertiary provinces of India that we have reviewed so far, from Sind to Burma, the transition from an earlier marine type of deposits to estuarine and fluviatile deposits of later ages must have been perceived. The passage from the one type of formation to the other was not simultaneous in all parts of the country, and marine conditions might have persisted in one part long after a fluviatile phase had established itself in another ; but towards the middle of the Miocene period the change appears to have been complete and universal, and there was a final retreat of the sea from the whole of

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north India. This change from the massive marine nummulitic lime­ stone of the Eocene age, containing abundance of foraminifera, corals and echinoids, to the river-deposits of the next succeeding age crowded with fossil-wood and the bones of elephants and horses, deer and hippopotami, is one of the most striking physical revolutions in India. We must now turn to the great system of Upper Tertiary riverdeposits which everywhere overlies the Middle Tertiary, enclosing in its rock-beds untold relics of the higher vertebrate and mammalian life of the time, comprising all the types of the most specialised mammals except Man. R EFE R E N C E S W. T. Blanford, Geology o f W. Sind, Mem. G .S.I. vol. xvii. pt. 1, 1879. G. E. Pilgrim, T ertiary Fresh-water Deposits of India, Rec. G .S.I. vol. xl. pt. 3 1910. F E. H. Pascoe, Oil-fields of India, Mem. G .S.I. vol. xl. 1912-1920; Rec. G .S.I. vol. xxxviii. pt. 4, 1910. P. M. Duncan and W. P. Sladen, T ertiary F auna of W. India, Pal. Indica, sers. vii. and xiv., vol. 1, pt. 3. G. E. Pilgrim, V etrebrate F auna o f the Bugti Beds, Pal. Indica, N.S., vol. iv. mem. 2, 1912. A. B. W ynne, Tertiaries of the Punjab, Rec. G .S.I. vol. x. pt. 3, 1877. E. S. Pinfold, Stratigraphy of N.W. P unjab, Rec. G .S.I. vol. xlix., 1918. G. do P. Cotter, Geology of the A ttock D istrict, Mem. G .S.I. vol. lv. pt. 2, 1933. P. Evans, T ertiary Succession in Assam, Trans. M in. and Geol. Inst. Ind. vol. xxvii., 1932.

CHAPTER XX T H E SIW A LIK SYSTEM

MIDDLE MIOCENE TO LOWER PLEISTOCENE General—Upper Tertiary rocks occur on an enormous scale in the extra-Peninsula, forming the low, outermost hills of the Himalaya along its whole length from the Indus to the Brahmaputra. They are known as the Siwalik system, because of their constituting the Siwalik hills near Hardwar, where they were first known to science, and from which were obtained the first palaeontological treasures that have made the system so famous in all parts of the world. The same system of rocks, with much the same lithological and palaeontological char­ acters is developed in Baluchistan, Sind, Assam, and Burma, forming a large proportion of the foot-hill ranges of these provinces. Local names have been given to the system in the extra-Himalayan areas, e.g. the Mekran system in Baluchistan, Manchar system in Sind, the Tipam and Dihing series in Assam, and the Irrawaddy system in Burma, but there is no doubt about the parallelism of all these groups. The Siwalik deposits—The composition of the Siwalik deposits |' shows that they are nothing else than the alluvial detritus derived from the subaerial waste of the mountains, swept down by their numerous rivers and streams and deposited at their foot. This pro­ cess was very much like what the existing river-systems of the Himal­ ayas are doing at the present day on their emerging to the plains of the Punjab and Bengal. An important difference is that the former alluvial deposits now making up the Siwalik system have been in­ volved in the latest Himalayan systems of upheavals by which they have been folded and elevated into their outermost foot-hills, although the oldest alluvium of many parts of northern India serves to some extent to bridge the gap between the newest Siwaliks and the present \ alluvium. The folding of the Siwalik sediments has imparted to them ' high dips and some degree of induration, both of which arc of course absent from the recent alluvial deposits of the plains of India. In the severe compression and stresses to which they have been 263

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subjected in the mountain-building processes, some of the folds have been inverted or reversed, with the overturning of the fold-planes to highly inclined positions. As is often the case with reversed folds, the middle limb of the fold (which has to suffer the severest tension), hav­ ing reached the limit of its strength, passed into a highly inclined frac­ ture or thrust-plane, along which the disrupted part of the fold has b

a

Ovecfold F ig . 30.—Diagrams to illustrate the formation of reversed faults in the

Siwalik zone of the Outer Himalayas.

slipped bodily over for long distances, thus thrusting the older preSiwalik rocks of the inner ranges of the mountains over the younger rocks of the outer ranges. / T h e geotectonic relations of the Siwaliks—These reversed overthrust faults are a characteristic and highly significant feature of the outer Himalayas; many of the reversed faults of the Siwalik zone can be traced for enormous distances. Wherever the Siwalik rocks are found in contact with the older formations, the plane of junction is always a reversed fault, with an apparent throw of many thousand feet, and along which the normal order of superposition of the rockgroups is reversed, the younger Siwalik beds resting under the older Sirmur and dipping under them. This plane of contact is known_as the Main Boundary Fault. This fault is a most constant feature of the structure of the Outer Himalayas along their whole length from the Punjab to Assam. The Main Boundary Fault—The Main Boundary is again not the only fault, but is one of a series of more or less parallel faults among the Tertiary zone of the outer Himalayas, all ol which exhibit the same tectonic as well as stratigraphic peculiarities, i.e. the fault

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has taken place along the middle-limb of the folds and the lower and older rocks are thrust above the upper and younger, viz. the Siwalik under the Middle and Lower Tertiary, and the latter underneath the still older strata of the middle Himalayas. The researches of Middlemiss and Medlicott in Himalayan geology have led to the suggestion that the Main Boundary is not of the nature of a mere ordinary dislocation which limits the boundary of the present distribution of the Siwaliks, but marks the original limiTof deposition of these strata against the cliff oFfoot o f the then existing mountains, beyondfwhich th ey did not extendTcould never, in ta ct, exfen37- Subsequent tcTtheirdeposition this boundary has been doubt­ less further emphasised by some amount of faulting. The other faults are also of the same nature, and indicate the successive limits of the deposition of newer formations to the south of, and against, the ad­ vancing foot of the Himalayas during the various stages of their eleva­ tion. This view of the nature of the Main Boundary will be made clearer by imagining that if the rocks of the Indo-Gangetic alluvium, at present lying against the Siwalik foot-hills, were to be involved and elevated in a further, future phase of Himalayan upheaval, they would exhibit much the same relations to the Siwalik strata as the latter do to the older Tertiary or these in turn do to the still older systems of the middle Himalayas. According to this view these reversed faults were “ not contemporaneous but successional ”, each having been pro­ duced at the end of the period during which beds immediately to the south of it were being deposited. The hypothesis is based on the sup­ position that nowhere do the Siwaliks overstep the Main Boundary Fault, or extend as outliers beyond it, except very locally. I t is held that if the faults had been in the main later than the deposition of the beds there would have been many outliers to the north. Such outliers have, however, been found in a few cases and the faults, which are found to be of the nature of overthrusts, have been proved to be of later date than the deposition of the Siwaliks and even subsequent to their plication. Again, this interpretation, though acceptable in a general way for large tracts of the western Himalayan foot-hills, is not applicable to the eastern Himalaya of Assam. Here the faults are not of the nature of “ boundary faults ” in the sense of Medlicott and Middlemiss, but are thrust-planes which have covered up some width of the Siwalik terrain in their southward advance. It is possible, therefore, that the evidence favouring the interpretation put forward by these distin­ guished geologists is capable of another interpretation. I t is now

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known that the overthrust faults may have a thrO\Y of many thou­ sands of feet and consequently in overthrust areas the progress of denudation will have removed great thicknesses of beds from the up­ throw side of the fault and it has been suggested that this, together with our still imperfect knowledge of the Tertiaries of the Himalayas, should also be taken into account in explaining the apparent restric­ tion of the Siwaliks to a limited zone. The palaeontological interest of the Siwalik system—The most notable character of the Siwalik system of deposits, and that which has invested it with the highest biological interest, is the rich collection of petrified remains of animals of the vertebrate sub-kingdom which it encloses, animals not far distant in age from our own times which, therefore, according to the now universally accepted doctrine of des­ cent, are the immediate ancestors of most of our modern species of land mammalia. These ancient animals lived in the jungles and swamps which clothed the outer slopes of the mountains. The more

F ig . 31.—Section to illustrate the relations of the outer Himalaya to tho older rocks of the mid-Himalaya (Kumaon Himalaya). L.S. Lower Siwalik sandstones. U.S. Upper Siwalik conglomerate. M.S. Middle Siwalik sand-rock. N . Older rocks. (After C. S. Middlemiss.)

durable of their remains, the hard parts of their skeletons, teeth, jaws, skulls, etc., were preserved from decay by being swept down in the streams descending from the mountains, and entombed in rapidly accumulating sediments. The fauna thus preserved discloses the great wealth of the Himalayan zoological provinces of those days, compared to which the present world looks quite impoverished. Many of the genera disclose a wealth of species, now represented by scarcely a third of that number, the rest- having become extinct. No other mammalian race has suffered such wholesale obliteration as the Proboscideans. Of the nearly thirty species of elephants and elephant-like creatures t hat peopled the Siwalik province of India, and were indigenous to it. only one is found living to-dav. The first discovered remains were obtained from the Siwalik hills near Hardwar in 1839, and the

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great interest Aflffch they aroused is evid­ ent from the following popular description by Dr. Mantell : “ Wherever gullies or fissures expose the section of the beds, abundance of fossil bones appear, lignite and trunks of dicotyledonous trees occur, a few land and fresh-water shells of existing species are the only vestiges of mollusca that have been observed. Remains of several species of river-fish have been obtained. The remains of elephants and of mastodontoid animals comprise perfect specimens of skulls and jaws of gigantic size. The tusks of one example are 9 feet 6 inches in length and 27 inches in circum­ ference at the base.1 This collection is invested with the highest interest not only on account of the number and variety of the specimens, but also from the extraordinary assemblage of the animals which it presents. In the sub-Himalayas we have entombed in the same rocky sepulchre bones of the most ancient extinct species of mammalia with species and genera which still inhabit India : Eleurogale, Hyaenodon, Dinotheria, mastodons, elephants, giraffes, hippopotami, rhinoceroses, horses, camels, antelopes, monkeys, struthious birds and crocodilian and chelonian reptiles. Among these mam­ malian relics of the past are the skulls and bones of an animal named Sivatherium that requires a passing notice. This creature forms, as it were, a link between the rum­ inants and the large pachyderms. It was larger than a rhinoceros, had four horns, 1This has been much exceeded in some later finds, e.g. a specimen discovered by the writer in the upper Siwalik beds near Jammu, in which the left upper incisor of Stegodon ganesa was found intact with the maxillary apparatus and the upper molars. The tusk measurod from tip to socket 10 ft. 7 in., the circum­ ference a t the proximal end being a little over 25 inches.

o , IB

Po

to

I

tr--*

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and was furnished with a proboscis, thus combii#i|; the horns-of a ruminant with the characters of a pachyderm. Among the reptilian remains are skulls and bones of a gigantic crocodile and of a land turtle which cannot be distinguished from those of species now living in India. But the most extraordinary discovery is th at of bones and portions of the carapace of a tortoise of gigantic dimen­ sions, having a length nearly 20 feet. I t has aptly been named the Colossochelys A tla s” j^ R a p id evolution of Siwalik fauna—After the first few glimpses of the mammalian fauna of the Tertiary era in the Bugti beds and that in the Perim Island, this sudden bursting on the stage of such a varied popu­ lation of herbivores, carnivores, rodents and of primates, the highest order of the mammals, must be regarded as a most remarkable in­ stance of rapid evolution of species. Many factors must have helped in the development ajad differentiation of this fauna ; among those Q) favourable conditions^the abundance of food-supply by a ricli angiospermous vegetationJJwhich flourished in uncommon profusion, and the presence of suitable physical environments, under a genial climate, in a land watered by many rivers and lakes, must have been the most prominent. This magnificent assemblage of mammals, however, was not truly of indigenous Indian origin ; it is certain that it received large acces­ sions by migration of herds of the larger quadrupeds from such centres as Egypt, Arabia, Central Asia and even from distant North America by way of the land-bridge across Alaska, Siberia and Mon­ golia. According to Pilgrim 1 our hippopotamus, pigs and probos­ cideans had their early origin in Central Africa, from where they radiated out and entered India during late Tertiary, through Arabia and Iran ; while the rhinoceros, horse, camel and the group of Pri­ mates, probably all originating in North America, had as their evolu- 1 tionary centres various intermediate countries in Central and Western Asia and were migrants to India through some passes on the north­ west or north-east of the rising Himalayan barrier. The elephant, like the horse, has been a world traveller and instead of the two solitary species inhabiting India and South Africa at the present day, it had in late Tertiary times spread to and peopled almost every country of the world except Australia. Among the lower Siwalik mammals there are forms, like the Sivatherium, which offer illustrations of what are called synthetic types 1 Proceedings, 12th Indian Science Congress, Benares, 1925.

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(generalised or ld^diflflK^itial types), i.e. the early primitive animals that combined ii^hem the characters of several distinct genera which sprang out of the*i in the process of further evolution. They were thus the common ancestral forms of a number of these later species which in the progress of time diverged more and more from the parent type. Lithology—The Siwalik system is a great thickness of detrital rocks,, such as coarsely-bedded sandstones, sand-rock, clays and conglo­ merates measuring between 15,000 and 17,000 feet in thickness. The bulk of the formation, as already stated, is very nearly alike to the materials constituting the modern alluvia of rivers, except that the former are somewhat compacted, have undergone folding and faulting movements, and are now resting at higher levels, with high angles of dip. Although local breaks exist here and there, the whole thickness is one connected and complete sequence of deposits, from the begin­ ning of the Middle Miocene to the close of the Siwalik epoch—Lower Pleistocene. The lower part, as a rule, consists of fine-grained micaceous sandstones, more or less consolidated, with interbedded shales of red and purple colours : silicified mono- and dicotyledonous wood and often whole tree-trunks are most abundant throughout the Siwalik sandstones, and leaf-impressions in the shales. The upper part is more argillaceous, formed of soft, thick-bedded clays, capped at places, especially those at the debouchures of the chief rivers, by an /exMteiely coarse boulder-conglomerate, consisting of large rounded bouiaers of siliceous rocks. The lithology of the Siwaliks suggests their origin ; they are chiefly the ^ater-worn debris of the granitic core of the central Himalaya, deposited in the long and broad valley of the “ Siwalik ” river (p. 40). The upper coarse conglomerates are the alluvial fans or talus-cones at*CTie emergence of the mountain streams ; the great thickness of clays and sands represents the silts and finer sediments of the rivers laid down in flood-plains ; while it is probable that the lower, e.g. Kamlial beds, were formed in the lagoons or estuaries of the isolated sea-basins that were left by the retreating sea as it was driven back by the post-Murree upheavals. These lagoons and estuaries gradually freshened and gave rise to fluviatile and then to subaerial conditions of deposition. The composition as well as the characters of the Siwalik strata everywhere bears evidence of their very rapid deposition by the rejuvenated Himalayan rivers, which entered on a renewed phase of activity consequent on the uplift of the mountains. There is

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very little of lamination to be seen in deposits ; the stratification of the coarser sediments is also v en ^ ru d e; the great thickness of clays and sands represents the silts ilia liner sediments of the rivers laid down in flood-plains; while current-bedding is universally present. There is again little or no sorting of grains in the sandstones, which are composed of unassorted sandy detritus derived from the Himalayan gneiss, in which many of its constituent minerals can be recognised, e.g. quartz, felspar, micas, hornblende, tourmaline, iragnetite, epidote, garnet, rutile, zircon, ilmenite, etc. [Under the direction of P. Evans a great deal of detailed examination of heavy mineral constituents of the Upper Tertiary sediments of India has been carried out. The results of several thousand analyses have afforded useful data regarding the distribution of hornblende, epidote, kyanite, staurolite, etc., which are likely to be of value for correlation purposes where other means such as fossils or stratigraphic proofs are not available.] The idea of the older geologists that the whole Siwalik system of rocks were deposits of the nature of alluvial fans, talus slopes, etc., at the debouchers of the Himalayan rivers very much along the sites of their present-day channels, does not appear to be tenable on the ground of the remarkable homogeneity that the deposits possess. Not only do they show on the whole uniformity of lithological compositia^at such distant centres as Hardwar, Simla hills, Kangra, Jam m irand Potwar, but also there is a striking structural unity of disposition along a definite and continuous line of strike. This negatives any theory of the deposition of these rocks in a multitude of isolated basins. The periodic uplift of the Himalayas, accompanied by theflhcroachment of the mountain-foot gradually towards the rapidly filling depression to the south resulted in the main drainage channels being pushed southwards. As the uplift proceeded, each periodic uprise of the mountains rejuvenated the vigorous young streams from the north, while the drainage from the south became enfeebled and dis­ organised so that in the building up of the Siwalik pile the sediments from the Gondwana mainland had but little share. Plow far south­ wards the Siwaliks extended is not certain, but it is highly probable that a considerable breadth of the Siwaliks lies buried under the alluvium of the Ganges. Classification—On palaeontological grounds the system is divisible

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into three sectioft, th e passage of the one into the other division

being, however, quite gradual and transitional: ' ™ 1_ Lower Boulder-conglomerate Coarse boulder-conPleisto­ glomcrates, thick zone : cene to earthy clays, sands, Elephas namadicus, Lower and pebbly grit, Equus, Camelus, Pliocene. passing up into Upper Buffelus palaeinolder alluvium. Siwalik, dicus. Richly fossili­ 6000Pinjor zone : ferous in the Si­ 9000 ft. E. planifrons, Ilemiwalik hills. bos, Stegodon. Tatrot zone : Ilippohyus, Leptobos. Grey and white sand­ Upper to Dhok Pathan zone : Middle stones and sandStegodon, Mastodon, Miocene rock with shales Hippopotamus, (Pontand clays of pale large Giraffoids, ian). and drab colours. Sus, MerycopotaMiddle Pebbly at top. mus. Siwalik, The richest Si­ 6000walik fauna occurs 8000 ft. in the Salt-Range. Massive, thick, grey Nagri zone: sandstones with M astodon, H ip p a rfewer shales and io n , Prostegodon. clays, mostly red coloured. Bright red nodular Middle Chinji stage: Miocene. shales and clays Listriodon, A m p h iwith fewer grey cyon, G iraffokeryx, sandstones and Tetrabelodon. pseudo- conglomer­ ates. Unfossili­ Lower ferous in the Si­ Siwalik, walik hills (Na(Nahari), 4000hans). Dark, hard sand­ 5000 ft. Kamlial stage: stones and red and Helvetian. A ceratherium , Telpurple shales and matodon, T etrabelo pseudo-conglomer­ don, A nthropoids, ates. Hyoboops. Fossiliferous in the Punjab. UpperConformable passage downwards into Upper Murree. Murree sandstones and shales.

(Burdigalian.)

The Potwar terrain immediately north of the Salt-Range and the

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Kangra-Hardwar tract may be regarded as type-aft as of the Siwaliks both as regards stratigraphy and faunas. ^Siw alik Fauna The Siwalik deposits enclose a remarkably varied and abundant vertebrate fauna in which the class Mammalia preponderate. The first collections were obtained from the neighbourhood of the Siwalik hills in the early thirties of the last century, and subsequent addi­ tions were made by discoveries in the other Himalayan foot-hills. It has been recently considerably enriched by discoveries in the Potwar and Kangra areas, by Dr. Pilgrim. He has brought to light, in a series of brilliant palaeontological researches, a number of rich mammaliferous horizons among these deposits, which are of high zoological and palaeontological interest. These have established the perfect uni­ formity and homogeneity of the fauna over the whole Siwalik pro­ vince, and have enabled a revised correlation of the system. The following is a list of the more important genera and species of Mam­ malia classified according to Dr. Pilgrim. J^TJpper Siwalik: Primates : Simia, Semnopithecus, Papio. ^ Carnivores.: Hyaenarctus sivalensis, Melivora, Mustela, Lutra, Canis, Vulpes, Hyaena, Crocuta, Panthera, Ursus, Hystrix, , Viverra, Machaerodus, Felis cristata. ^ / y 1/ ^ Elephants : Mastodon sivalensis, Stegodon ganesa, S. clifti, S. insignis, Elephas planifrons, E. hysudricus, E. namadicus. Ungulates : Rhinoceros palaeindicus, Equus sivalensis, Sus falconeri, Hippopotamus f Camelus antiquus, Giraffa, Indr ather­ ium, Sivatherium giganteum,. Cervus, Moschus, Buffelus pal­ aeindicus, Bucapra, Anoa, Bison, Bos, Hemibos, Leptobos. Middle Siwalik : Primates : Palaeopithecus, Semnopithecus, Dryopithecus, Ramapithecus sp., Sugrivapithecus, Cercopithecus, Macacus. Carnivores : Hyaenarctos, Indarctos, Palhyaena, Mellivorodon, Lutra, Amphicyon, Machaerodus, Felis. Eodents : Hystrix.

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Elephants : Dinotherium, Tetrabelodon, Prostegodon cautleyi and latidens, Stegodon clifti, Mastodon hasnoti. Ungulates : Teleoceras, Aceratherium, Hipparion (very common), Merycopotamus, Tetraconodon, Hippohyus, Potamochoerus, Listriodon, Sus punjabiensis, Hippopotamus irravaticus, Dorcatherium, Tragulus, Hydaspitherium, Aceratherium, VishnutJu ri im, Cervus simplicidens, Gazella, Tragoceras, Anoa. Lower§iwalik: Primates : Sivapithecus indicus, Dryopithecus, Indraloris, Bnimzpithecus, Palaeosimia. Carnivores : Dissopsalis, Amphicyon, Palhyaena, Vishnufelis. Proboscidians : Dinotherium, Trilopliodon. Ungulates : Aceratherium, Hyotherium, Anthracotherium, Dorcabune, Dorcatherium, Hemimeryx, Brachyodus, Hyoboops, Girajfokeryx, Conoliyus, Sanitherium, Listridon, Telmatodon. Besides these the lower vertebrate fossils are : Birds : Phalacrocorax, Pelecanus, Struthio, Mergus. Reptiles : (Crocodiles) Crocodilus, Gharialis, Rhamphosuchus; (Lizard) Varanus; (Turtles) Colossochelys atlas, Bellia, Trionyx, Chitra ; Snakes, Pythons. Fish : Ophiocephalus, Chrysichthys, Rita, Arius, etc. Special interest attaches to the occurrence of about eleven genera^f fossil primates m the Siwalik group. These fossils furnish important material faTtKe study of the evolution of the highest order of Mammals, the phylogeny of the living anthropoid apes, and the probable fines of human ancestry. A most interesting and representative collection of the Siwalik fossils of India is arranged in a special gallery, the Siwalik gallery, in the Indian Museum, Calcutta. Age of the Siwalik system—From the evidence of the stage of evolution of the various types composing this fauna, and from their affinity to certain well-established mammaliferous horizons of Europe, which have furnished indubitable evidence of their age because of their interstratification with marine fossiliferous beds, the age of the Siwalik system is determined to extend from the Middle Miocene to

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the Lower and even Middle Pleistocene. The Middle Siwaliks are believed to be homotaxial with the well-known Pikermi series of Greece, of Pontian, i.e uppermost Miocene, age. A parajlel series of deposits is developed in other parts of the extra-Peninsula, as already alluded to. These have received local names but they are in most cases also fluviatile or sub-aerially deposited sandstones, sand-rock, clays and conglomerates, contain­ ing abundance of fossil-wood and (in some areas) mammalian remains agreeing closely with the Siwaliks. v/M ekran system —The Mekran system in Baluchistan differs from tlie equivalents in other areas in having marine fossils. I t includes a great thickness of sandstones and shales and towards the top of the succession are pebble beds which correspond approximately to the Upper Siwaliks. The occurrence of a marine fauna in the Mekran system is a feature of some importance but sufficient work has not yet be^n done to enable a detailed succession to be made out. -/M anchar system —In Sind the Manchar system has been divided into a lower group which is fossiliferous and is equivalent to the fossiliferous beds of the Potwar from the base of the Siwaliks to the Dhok Pathan zone, and an upper group which probably corresponds to the uppermost portion of the Upper Siwaliks. / Tipam and Dihing series—In Assam the Siw^alik system is approxi­ mately equivalent to the Tipam and Dihing series. The Tipam series consists typically of coarse ferruginous sandstones and mottled clay, becoming conglomeratic towards the top. I t overlies with apparent conformity the Lower Miocene Surma series and presumably corres­ ponds with either the Lower or Middle Siwaliks, but owing to the paucity of fossils no precise correlation is possible. The Dihing series consists mainly of pebble beds resting unconformably on the Tipam series. These deposits presumably correspond to the Upper Siwaliks. Irrawaddy system —In Central Burma, the lower portion of the Siwalik system appears to be missing and there is a pronounced break between the Upper Pegus of Lower Miocene age and the overlying Irrawaddy system of Upper Miocene to Pliocene age. The Irrawaddy system is made up largely of coarse, current-bedded sands and occasional beds of clay and conglomerate with locally at the base a conspicuous “ red-bed ” of lateritic origin. The total thickness may reach 10,000 ft. Two fossiliferous horizons occur in this series, separated by about 4000 ft. of sands. The lower, containing Ilipparion and Aceratherium,, denotes the Dhok Pathan horizon of the SaltRange, while the upper, characterised by species of Mastodon,

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Stcgodon, Hippopotamus and Bos, is akin to the Tatrot zone of Upper Siwaliks. The sediments are remarkable for the large quantities of fossil-wood associated with them and they were originally known as the “ fossil-wood group ”. Hundreds and thousands of entire trunks of silicified trees and huge logs lying in the sandstones suggest the denudation of thickly forested eastern slopes of the Arakan Yoma. Further north in Burma it is probable that the Irrawaddy system ex­ tends to somewhat lower horizons than in Central Burma and the boundary between the Pegu and Irrawaddy rocks is often difficult to fix. R EFE R E N C E S H. Falconer and P. T. Cautley, Fauna Antiqua Sivalensis, 1846, London. G. E. Pilgrim, Correlation of the Siwalik Mammals, Rec. G .S.I. vol. xliii. pt. 4, 1913 ; T ertiary Fresh-water Deposits of India, Rec. G .S.I. vol. xl. pt. 3, 1910. R. D. Lydekker, Siwalik Fossils, Pal. Indica, series x. vols. i. ii. iii. iv. G. E. Pilgrim, Pal. Indica, N.S. : Fossil Giraffidae, vol. iv. mem. 1, 1911; Fossil Suidae, vol. viii. mem. 4, 1926 ; Fossil Carnivora, vol. xviii, 1932 ; Fossil Bovidae, under preparation. C. S. Middlemiss, Geology of the Sub-Him alayas, Mem. G .S.I. vol. xxiv. pt. 2, 1890. A. B. W ynne, Rec. G .S.I. vol. x. pt. 3, 1877. D. N. Wadia, Siwaliks of Potw ar and Jam m u Hills, Mem. G .S.I. vol. li. pt. 2, 1928. E. H. Colbert, Siwalik Mammals, Trans. Amer. Phil. Soc., N.S., vol. xxvi., 1935.

T H E PLE IST O C E N E SYSTEM

CHAPTER XXI T H E PLEISTO CEN E SYSTEM

y . THE GLACIAL AGE IN INDIA The Pleistocene or Glacial Age of Europe and America—The close of the Tertiary era and the commencement of the Quaternary is marked in Europe, North~America and the northern world generally, ~by a great refrigeration of cE^aate, culminating In what is known as the Ice Age or Glaohd-A ffe^i^e glacial conditions~prevailed~so"Tar south asj39° latitude north, and countries which now experience a temperate climate then experienced j h e arctic coldof the polar regions, and were covered under ice-sheets radiating from th e higher grounds. The evidence fo rth is^ reafch an g eln the climatic conditions of the globe is of the most convincing nature, and is preserved both in the physical records of the age, e.g. in the characteristic glaciated topography ; the “ glacial drift ” or moraine-deposits left by the glaciers ; and the effects upon the drainage system of the countries, as well as in the organic records, e.g. the influence of such a great lowering of the temperature on the plants and animals then living ; on the migra­ tion or extinction of species and on their present distribution. V A modified Glacial Age in India—Whether India, that is, parts lying to the south of the Himalayas, passed through a Glacial Age, is an interesting though an unsettled problem^ In India, it must be under­ stood, we cannot look for the actual existence of ice-sheets during the Pleistocene gtecial epoch, because a refrigeration which can produce glacial conditions in Northern Europe and America would not, the present zonal distribution of the climate being assumed, be enough to depress the temperature of India beyond th at of the present temperate zones. Hence we should not look for its evidence in moraine-de bris and rock-striations (except in the Himalayas), but in the indirect y organic evidence of the influence of such a lowering of the temperature and the consequent increase of humidity, on the plants and animals then living in India. Humidity or dampness of climate has been found to possess as much influence on the distribution of species in 276

277

India as temperature. LFrom this point of view sufficient evidence, exists of the glacial cold of the northern regions being felt in the plains//] of India, though to a much less extent, in times succeeding the Siwalilc epoch after the Himalayan range had attained its full elevation. ' The great Ice Age of the northern world was experienced in thfcjj southerly latitudes of India as a succession of cold pluvial epochs. \i^The nature of the evidence for an Ice Age in the Peninsula—This evidence, derived from some peculiarities in the fauna and flora of the hilts and mountains of India and Ceylon, is summarised by W. T. Blanford—one of the greatest workers in the field of Indian geology and natural history. several isolated hill ranges, such as the Nilgiri, Animale, Shivarai and other isolated plateaus in Southern India, and on the mountains of Ceylon, there is found a temperate fauna and flora which does not exist in the low plains of Southern India, but which isjcloselv allied to the temperate fauna and flora of ffimn.laya.sthe Assam Range, the mountains of the Malay Peninsula and Java. Even on isolated peaks such as Parasnath, 4500 feet high, in Behar, and on Mount Abu in the Aravalli Range, Rajputana, several Hima­ layan plants exist. I t would take up too much space to enter into details^) The occurrence of a Himalayan plant like Rhododendron arboreum and of a Himalayan mammal like Martes jlavigula on both the Nilgirisland Ceyloif'mountains will serve as an example of a considerable number of less easily recognised species. In some cases there is a closer resemblance between the temperate forms found on the Peninsular hills and those on the Assam Range than between the former and Himalayan species, but there are also connections be­ tween the Himalayan and the Peninsular regions which do not extend to the eastern hills. i^jTte most remarkable of these is the occurrence on the Nilgiri and Animale ranges, and on some hills further south, of a species of wild goat, Capra hylocriusx belonging to a sub-genus (Hemitragus) of which the only known species, Capra Jeemlaica, inhabits the temperate regions of the Himalayas from Kashmir to Bhutan. This case is remarkable because the only other wild goat found completely outside the palaearctic region is another isolated form in the moun­ tains of Abyssinia. x “ The .range in_devation of the temperate flora and fauna of the Oriental regions in general appears to depend more on humidity t han t emperature, many of the forms which in the Indian hills are peculiar to the higher ranges being found represented by the allied species at lower elevations in the damp Malay Peninsula and Archipelago, and

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some of the hill forms being even found in the damp forests of tlie Malabar coast. The animals inhabiting the Peninsula and Ceylonese hills belong for the most part to species distinct from those found in the Himalayan and Assam ranges, etc., in some cases even genera are peculiar to the hills of Ceylon and Southern India, and one family of snakes is unrepresented elsewhere. There are, however, numerous plants and a few animals inhabiting the hills of Southern India and Ceylon which are identical with Himalayan and Assamese hill forms, but which are unknown throughout the plains of India. “ That a great portion of the temperate fauna and flora of the Southern Indian hills has inhabited the country from a much more dis­ tant epoch than the glacial period may be considered as almost cer­ tain, there being so many peculiar forms. I t is possible that the species common to Ceylon, the Nilgiris and the Animale may have migrated a t a time when the country was damper without the temperature being lower, but it is difficult to understand how the plains of India can have enjoyed a damper climate without either depression, which must have caused a large portion of the country to be covered by sea, a diminished temperature, which would check evaporation, or a change in the prevailing winds. The depression may have takenj>lace, I but the migration of the animals and plants from the Himalayas to Ceylon would have been prevented, not aided, by the southern area being isolated by the sea, so th at it might be safely inferred th at the period of migration and the period of depression were not contempor­ aneous. A change in the prevailing winds is improbable so long as the present distribution of land and water exists, and the only remaining t heory to account for the existence of the same species of animals and plants on the Himalayas and the hills of southern India is depression lof tem perature/* Ice Age in the Himalayas—When, however, we come to the Hima­ layas, we stand on surer ground, for the records of the glacial age there are unmistakeable in their legibility. At many parts of the Himalayas there are indications of an extensive glaciation in the im­ mediate past, and that the present glaciers, though some of them are among the largest in the world, are merely the shrunken remnants of those which flourished in the Pleistocene age. Enormous heaps of terminal moraines, now grass-covered, and in some cases treecovered, ice-transported blocks, and the smoothed and striated hummocky surfaces and other indications o f the action of ice on land surface are observed at all parts of the Himalayas that have been explored from Sikkim to Kashmir at elevations several thousand feet

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below the present level of descent of the glaciers. On the Haramukh mountain in Kashmir a mass of moraine is described at an elevation of 5500 feet. Grooved and polished rock-surfaces have been found at Pangi in the Upper Chenab valley, and at numerous localities in the Sind and Lidar valleys, on cliff-faces at 7500 feet level. In the Pir Panjal, above 6500 feet, the mountains have a characteristic glaciated aspect, while the valleys are filled with moraines and fluvio-glacial drift. On the southern slopes of the Dhauladhar range an old moraine (or what is believed to be such) is found at such an extraordinarily low altitude as 4700 feet, while in some parts of Kangra, glaciers were at one time believed, though not on good evidence, to have descended below 3000, feet level. In Southern Tibet similar evidences are numerous at the lowest situations of that elevated plateau. Equally convincing proofs of ice-action exist in the interruptions to drainage courses that were caused by glaciers in various parts of the mountains. Numerous small lakes and rock-basins in Kashmir, Ladakh and , Kumaon directly or indirectly owe their origin to the action of glaciers now no longer existing. A more detailed survey and exploration of the Himalayas than has been possible hitherto will bring to light further proofs. The ranges of the Middle Himalayas, which support no glaciers to­ day, have, in some cases, their summits and upper slopes covered with moraines. The ice-transported blocks of the Potwar plains in Attock and Rawalpindi (referred to on page 303) also furnish corroborative evidence to the same effect. (Note also the testimony of some hang­ ing valleys (p. 21), and of the well-known desiccation of the Tibetan lakes (p. 22).) The extinction of the Siwalik mammals—one further evidence— Further evidence, from which an inference can be drawn of an Ice Age in the Pleistocene epoch in India, is supplied by the very striking circumstance to which the attention of the world was first drawn by the great naturalist/Alfred R.nssp.1 Wallace^ wThe sudden and wide­ spread reduction, by extinction, of the Siwalik mammals is a most startling event for the geologist as well as the biologist The great Carnivores, the varied races of elephants belonging to no less than twenty-five to thirty species, the Sivatherium and numerous other tribes of large and highly specialised Ungulates which found such suitable habitats in the Siwalik jungles of the Pliocene epoch, are to be seen no more in an immediately succeeding age.v/This sudden dis­ appearance of the highly organised mammals from the fauna of the world is attributed by the great naturalist to the effect of the intense

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SIWALIKS

c3 .2 £

UPPER

o to CO © w V o p£pj > ce 'V ^ c3 © M 5 >> Satpura fields 30 Ballalpur-Singareni fields 50

341

feet from the surface. Over a hundred million tons of moderategrade lignite is easily recoverable from one area. The percentage of combustible matter is generally about 55.1 PEAT The occurrence of peat in India is confined to a few places of high elevation above the sea. True peat is found on the Nilgiri mountains in a few peat-bogs lying in depressions composed of the remains of Bryophyta (mosses). In the delta of the Ganges, there are a few layers of peat composed of forest vegetation and rice plants. In the numer­ ous Jhils of this delta peat is in process of formation at the present day and is used as a manure by the people. Peat also occurs in the Kashmir valley in a few patches in the alluvium of the Jhelum and in swampy ground in the higher valleys ; it is there composed of the debris of several kinds of aquatic vegetation, grasses, sedges and rushes. Similar deposits of peat are in course of formation in the valley of Nepal. The chief use of peat is as a fuel, after cutting and drying. I t is also employed as a manure. \ / PETROLEUM

9

yy

Total

5000

yy

yy

Reserves of good coking Coal Giridih f i e l d ...............................................30 million tons Raniganj fie ld ............................................... 250 „ „ Jharia field -* - 900 „ „ Bokaro f i e l d ............................................... 320 „ „ Karanpura field not estimated Total

-

-

1500 million tons

The hitherto coal-less area of Kashmir has lately been found to possess fuel deposits of considerable size, belonging to Pliocene or even newer age. Thin seams of brown coal or lignite occur inter­ stratified with the top beds of the older Karewa series within a few 1 Mem. O.S.I. vol. lix, 1934.

Distribution of Oil—The occurrence of petroleum in India is re­ stricted to the extra-Peninsula, where it is found in Tertiary rocks of ages ranging from Lower Eocene to Middle Miocene.2 There are three regions in w^hich oil production has been obtained. The most im­ portant is the Chindwin-Irrawaddy valley of Burma ; to the west lies the Assam-Arakan oil belt stretching from Upper Assam southwestwards through the Surma valley and Chittagong to the Arakan coast. In North West India, oil indications have been observed in Baluchistan, the Punjab,3 and the N.W7. Frontier Province. Burma—In Burma, there are oil and gas seepages in the upper half of the Eocene and in the Pegu rocks (Oligocene to Miocene). The oil­ fields are situated on anticlines in which the porous sands interbedded with impervious clays present favourable conditions for the accumu­ lation and storage of oil. The fields are situated in a belt which closely follows the line of the Chindwin and Irrawaddy. In the Yenangyaung 1 C. S. Middlemiss, Rec. G.S.I. vol. Iv. pt. 3, 1924. 2 E. H. Pascoe, Oil-fields of India, Mem. G.S.I. vol. xl, 1911-1920. 8 E. S. Pinfold, Occurrence of Oil in the Punjab, Journ. Asiat. Soc. Beng., N.S. vol. xiv, 1918,

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field (Magwe district), production is obtained mainly from the Lower Miocene and Upper Oligocene ; in the more northern fields of Singu (Magwe district), Lanywa, and Yenangyat (Pakokku district) the production is from the Oligocene.1 Yenangyaung yields about 130 million gallons a year and Singu about 80 million gallons. Lanywa and Yenangyat in the Pakokku district together produce about 20 million gallons per year. Further south in the Minbu district small fields yield about 3 to 4 million gallons annually. ' Assam—In Assam, oil seepages occur in rocks ranging from Eocene to probably Middle Miocene. The only productive field is Digboi, in the Lakhimpur district, where the annual yield has in recent years come up to about 60 million gallons. The Badarpur field which at one time yielded about 4 million gallons annually, became exhausted in 1933, but exploratory drilling has been continued in neighbouring anticlines. Further south, on the Arakan coast, although there are numerous oil and gas shows, the production of oil is negligible. North West India—Oilshows occur in various districts along the North-Western Frontier, particularly in the Potwar region. Most of the oil-shows are in the lower part of the Chharat series (Laki) or in the basal beds of the overlying Murrees or Siwaliks. In spite of energetic prospecting of large areas the only commercially productive field is a t Khaur in the Attock district. The output reached a maximum of 19 million gallons in 1929 but subsequently declined to about 4 million gallons. Lately successful boring to a depth of 7100 ft. in the adjacent Dhulian dome has increased the production again. Although the Khaur production has come from the Murree series, it is believed th at the origin is in the underlying Eocene rocks from which the oil has migrated upwards. The deeper drilling has recently proved the occurrence of oil and gas in the Eocene limestones here and in the neighbouring Dhulian area. Natural Gas—Natural gas (chiefly marsh gas with some other gaseous hydrocarbons) usually accompanies the petroleum accumu­ lations.2 The gas may occur in separate sands containing little or no oil, but most of the natural gas of India is found closely associated with the oil, and supplies the propulsive force which carries the oil from the oilsands into the wells and, if the pressure is sufficient, brings the oil up to the surface. Since gas is essential for the production of the oil and is also valuable as a source of fuel on the oilfields, care is taken 1 G. W. Lepper, Proc. World Petrol. Cong., 1933; P. Evans, Trans. Min. Oeol. hist. Ind. vol. xxix. pt. 1, 1934. 2 C. T. Barber, Natural Gas Resources of Burma, Mem. G.S.I. vol. lxvi. pt. 1, 1935.

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to prevent the waste of gas, which was formerly so common in the oilfields. The total contribution to world supply of petroleum by India and j Burma is rather over 300 million gallons per year and this represents only 0-6 per cent of the total world output. In addition to the oil produced in India and Burma, about 200 million gallons are imported from foreign countries. 6. METALS AND ORES General. Neglect of ore-bodies in India—India contains ores of manganese, iron, gold, aluminium, lead, copper, tungsten, tin, chrom­ ium, and a few other metals in minor quantities, associated with the crystalline and older rocks of the country. In the majority of the cases, however, the ore bodies are worked, not for the extraction of the metals contained in them, but for the purpose of exporting the ores as such in the raw condition, since few smelting or metallurgical opera­ tions are carried on in the country at the present time. For this reason the economic value of the ores realised by the Indian miners is barely half the real market-value, because of the heavy cost of trans­ port they have to bear in supplying ores to the European manufac­ turer at rates current in the latter’s country. The absence of metal­ lurgical enterprise in this country a t the present day has led to a total neglect of its ore-deposits, except only those whose export in the raw condition is paying. This is a serious drawback in the development of the mineral resources of India, the cause for which lies in the present imperfect and undeveloped state of the country’s industries. Sir T. H. Holland, in his review of the mineral production of India, pointed out in 1908 th at the “ principal reason for the neglect of the metalliferous minerals is the fact that in modern metallurgical and chemical developments the bye-product has come to be a serious and indispensable item in the sources of profit, and the failure to use the bye-product necessarily involves neglect of minerals that will not pay to work for the metal alone. Copper-sulphide ores are conspicuous examples of the kind ; many of the most profitable copper mines of the world would not be worked but for the demand for sulphuric acid manufacture, and for sulphuric acid there would be no demand but for a string of other chemical industries in which it is used. A country like India must be content, therefore, to pay the tax of imports until in­ dustries arise demanding a sufficient number of chemical products to complete an economic cycle, for chemical and metallurgical industries

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are essentially gregarious in their habits.” Many of the ore-deposits of India, although of no economic value under the conditions prevail­ ing at the present day, are likely to become so at a future day when improved methods of treatment and better industrial conditions of the country may render the extraction of the metals more profitable. From this consideration the large yearly exports of such ores as manganese out of India are doubly harmful to the interests of the country.

cru sh e d quartz, and stone-mortars, which have (as has often hap­

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Gold Occurrence—Gold occurs in India, both as native gold, associated with quartz-veins or reefs, and as alluvial or detrital gold in the sands and gravels of a large number of rivers. The principal sources of the precious metal in India, however, are the quartz-reefs traversing the Dharwar rocks of Kolar district (Mysore State), which are auriferous at a few places.1 The auriferous lodes of the Kolar goldfields are con­ tained in the above-mentioned quartz-veins, which run parallel to one another in a north-south direction in a belt of hornblende-schists. The most productive of these is a single quartz-vein, about four feet thick, which bears gold in minute particles. Mining operations in this reef have been carried to a depth of 7400 feet, one of the deepest mining shafts in the world, and have disclosed continuance of the same rich­ ness and method of distribution of the ore in the gangue. LThe gold is obtained by crushing and milling the quartz, allowing the crushed ore mixed with water to run over mercury-plated copper boards. The greatest part of the gold is thus dissolved by amalgamation. The small residue that has escaped with the slime is extracted by the cyanide process of dissolving gold. Production of vein-gold—The annual yield of gold from the Kolar fields is nearly 340,000 ozs., valued, at the present price of gold, at more than £2,000,000. Next to Kolar, but far below it in productiveness, is the H utti gold-field of the Nizam’s dominions, which was also worked from a similar outcrop of Dharwar schists. I t produced 21,000 ozs. of gold in 1914, but the output fell off and the mine has been closed. A few quartz-veins traversing a band of chloritic and argillaceous schists, also of Dharwar age, support the Anantpur field of Madras, whose yield in 1915 approached 24,000 ozs. This mine ceased operations after several vicissitudes in 1927. At some other places in the Penin­ sula, besides those named above, the former existence of gold is re­ vealed by many signs of ancient gold-working in diggings, heaps of 1 Kolar Gold-Field, Mem. G.S.I. vol. xxxiii. pts. 1 and 2, 1901.

pened in India with regard to other metalliferous deposits) guided the attention of the present workers to the existence of gold. Alluvial gold—The distribution of alluvial gold in India is much wider. Many of the rivers draining the crystalline and metamorphic tracts in India and Burma are reputed to have auriferous sands, but only a few of them contain gold in a sufficient quantity to pay any commercial attem pt for its extraction. The only instance of success­ ful exploitation of this kind is the dredging of the upper Irrawaddy valley for the gold-bearing gravel at its bed, for some years ; but the returns fell off and operations were closed down in 1918. In this way some 5000 to 6000 ozs. of gold was won a year. Alluvial gold-washing is carried on in the sands and gravels of many of the rivers of the Central Provinces, and in sections of the Indus valley at Ladakh, Baltistan, Gilgit, Attock, etc., but none of them are of any richness comparable to the above instance. The quantity won by the indigent workers is just enough to give them their day’s wages with only occasional windfalls. Copper Occurrence—Copper occurs in some districts of India—Singhbhum, Chota Nagpur, etc. ; in Rajputana—Ajmere, Khetri, Alwar, Udaipur, and at several places in the outer Himalayas, in Sikkim, Kulu, Garhwal, etc. But the only deposits worked with some degree of success are those of the Singhbhum district, Mosaboni mines, which yield about 180,000 tons of ore per year, valued at Rs. 25 lacs. In 1934, 6300 tons of refined copper was produced from the ore mined at Mosaboni, the most important copper mines in India. In Singhbhum the copperbearing belt of rocks is persistent for about 80 miles along a zone of overthrust in the Dharwar schists and intrusive granite. The de­ posits worked at the Mosaboni mines consist of low-grade sulphide ore assaying 2-4% of copper. Somewhat richer ore-shoots have been located lately in the vicinity.1 There was a flourishing indigenous copper-industry in India in former years, producing large quantities of copper and bronze from the Rajputana, Sikkim, and Singhbhum mines, the sites of which are indicated by extensive slag-heaps and refuse “ coppcr-workings ”. Im portant copper-mines existed in Ajmere and in Khetri (in the Jaipur State) within historic times. Copper ore is found at Bawdwin in the Northern Shan States of 1J. A. Dunn, Mineral Deposits of Eastern Singhbhum, 1937.

Mem. O.S.I. vol. Ixix. pt,

1,

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Every year India imports iron and steel materials (hardware, machinery, railway plant, bars and sheets, etc.) to the value of nearly 32 crores of rupees. Distribution—A list of localities which contain the most noted de­ posits of iron ore will be interesting. In the Madras Presidency the most important deposits are those of Salem, Madura, Mysore (Bababudan hills), Cuddapah and Karnul, while Singhbhum, Manbhum, Burdwan, Sambalpur and Mayurbhanj are the iron-producing districts of Bihar and Orissa. In Bengal pro­ per, the Damuda ironstone shales contain a great store of metallic wealth, which has been profitably worked for a long time, both on account of its intrinsic richness as well as for its nearness to the chief source of fuel. In Assam also iron occurs with coal. In the Central Provinces the most remarkable iron deposit is th at of the Chanda district, where there is a hill 250 feet high, Khandeshwar by name, the entire body of which is iron ore. Jabalpur, Drug, Raipur, and Bhilaspur have likewise large aggregates of valuable haematitic ores which have been so far prospected only in part. In Bombay the chief source of iron is laterite and the magnetite-sands of rivers draining the trap districts, both of which are largely drawn upon by the itinerant lohars. Important reserves of high-grade ores of Dharwar age are met with in Goa and Ratnagiri, with low percentage of silica and of phosphorus below the Bessemer limit. In the Himalayas the Kumaon region has been known to possess some deposits. Workable iron-ore is met with in the Riasi district, Jammu hills, in association with the Nummulitic series, which supported a number of local furnaces for the manufac­ ture of munitions of war during the last two centuries. Manganese Production of manganese in India—With the exception of Russia (the Caucasus), India is the largest producer of manganese in the world. Within the last thirty years, the export of manganese ore has risen from a few thousand tons to 900,000 tons annually. The output has fallen in recent years to 550,000 tons. The major part of this out­ put is exported in the ore condition, only a small part of it being ctated in the coruntry for the production of the metal, or for its manuafterure into fero-manganese, the principal alloy of manganese and iron. Distribution. Geographical—The chief centres of manganese mining, or rather quarrying (for the method of extraction up till now resorted

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to is one of open quarrying from the hillsides), are the Balaghat, Bhandara, Chhindwara, Jabalpur and Nagpur districts of the Central Provinces, which yield nearly GOper cent, of the total Indian output. Sandur and Vizagapatan in Madras take the next place, then come the Panch Mahal and Belgaum districts of Bombay, and Singhbhum, Keonjhar and Gangpur in Bihar and Orissa, Chitaldrug and Shimoga districts of Mysore, and Jhalna in Central India. Geological—Dr. Fermor has shown th at manganese is distributed, in greater or less proportion, in almost all the geological systems of India, from the Archaean to the Pleistocene, but the formation which may be regarded as the principal carrier of these deposits is the Dhar­ war. The richly manganiferous facies of this system—the Gondite and Kodurite series—contain enormous aggregates of manganese ores such as psilomelane and braunite, pyrolusite, hollandite, etc. Of these the first two form nearly 90 per cent, of the ore masses. The geological relation of the ore bodies contained in these series and their original constitution have been referred to in the chapter on the Dharwar system (p. 80). Besides the Dharwar system, workable manganese deposits are contained in the lateritedike rock of various parts of the Peninsula, where the ordinary Dharwar rocks have been metasomatically replaced by underground water containing manganese solu­ tions. According to the mode of origin, the two first-named occur­ rences belong to the syngenetic type of ore bodies, i.e. those which were formed contemporaneously with the enclosing rock, while the last belong to the epigenetic class of ores, i.e. those formed by a process of concentration at a later date. A voluminous memoir on the manganese-ore deposits of India byi Dr. (now Sir) L. L. Fermor, published by the Geological Survey of India,1 contains valuable information on the mineralogy, economics and the geological relations of the manganese of India. Ores which contain from 40 to 60 per cent, of manganese are com­ mon and are classed as manganese ores. There also exist ores with an admixture of iron of from 10 to. 30 per cent. : these are designated ferruginous manganese ores ; while those which have a still greater proportion of iron in them are known as manganiferous iron ores. The average cost of Indian manganese ore delivered in London is less than Rs. 30 per ton of first grade ore, i.e. with a manganese percentage greater than 50. Uses—The chief use of manganese is in metallurgy for the manu­ facture of ferro-manganese and spiegeleisen, both of w^hich are alloys 1 Mem. O.S.I. vol. xxxvii. 1909.

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of manganese and iron. Manganese is employed in several chemical industries as an oxidiser, as in the manufacture of bleaching powder, disinfectants, preparation of gases, etc. Manganese is employed in the preparation of colouring materials for glass, pottery-paints, etc. The pink mineral, rhodonite (silicate of manganese), is sometimes cut for gems on account of its attractive colour and appearance.

cement. The present output of Indian bauxite is insignificant and is chiefly consumed in the cement-making industry, refine­ ment of oil, etc.

' Aluminium Bauxite in laterite—Since the discovery th at much of the clayey portion of laterite is not clay (hydrated silicate of alumina), but the simple hydrate of alumina (bauxite), much attention has been directed to the possibility of working the latter as an ore of alumin­ ium.1 Bauxite is a widely spread mineral in the laterite cap of the Peninsula, Assam and Burma, but the laterites richest in bauxite are those of the Central Provinces, especially of Katni, and of some hill­ tops in the Balaghat district in which the percentage of alumina is more than 50. Other important deposits are those of Mandla, Seoni, Kalahandi, Sarguja, Mahabaleshwar, Bhopal and the Palni hills and some parts of Madras. The total quantity of ore available from these jf deposits is very large, obtainable by simple methods of surface quarryfl ing. Extensive deposits of bauxite and aluminium ore, analysing 60 to 80 per cent. A120 3, have been discovered in association with the Nummulitics of Jammu and Poonch, where some million tons of ore is ex­ posed in surface strata. Their mode of occurrence also suggests a lateritic origin, e.g. by a desilication of large, subaerially exposed, spreads of infra-Nummulitic clay-beds on a-series of low, gently in­ clined dip-slopes. With deposits of the ore so wide-spread and of such magnitude the aluminium resources of India should be considered large, but so far no reduction of the bauxite to metallic aluminium has been carried out in India. The average annual imports of aluminium metal goods into India come to about 100,000 cwts. Uses—Aluminium has a variety of applications in the modern in­ dustries. It is esteemed on account of its low density, its rigidity and malleability. Besides its use for utensils, it has many applications in electricity, metallurgy, aeronautics, etc. I t is largely employed in the manufacture of alloys with nickel, copper, zinc and magnesium, in the preparation of chemicals, refractories, abrasives, and aluminous 1 C. S. Fox, Aluminous Laterites, Mem. O.S.I. vol. xlix, 1923; Bauxite Resources of India, Mining Magazine, vol. xxvi. Feb. 1922; Bauxite and Aluminous Laterite, London, 1932; Coggin Brown, Bulletin of I. I. and L. No. 2, 1921 ; No. 12, 1921.

Lead, Silver, Zinc Very little lead is produced in India at the present time, though ores of lead, chiefly galena, occur at a number of places in the Hima­ layas, Madras, Rajputana and Bihar, enclosed either among the crystalline schists or, as veins and pockets, in the Vindhyan lime­ stones. Lead was formerly produced in India on a large scale. The lead ores of Hazaribagh, Manbhum and some districts of the Central Provinces are on a fairly large scale, and they are often argentiferous, yielding a few ounces of silver per ton of lead. But all of these are lying unworked ; their remunerative mining is impossible because of the cheap price of imported lead. Lead ores of Bawdwin—The only locality where a successful lead industry 1 exists is Bawdwin in the Northern Shan States of Upper Burma, where deposits of argentiferous galena occur on an extensive scale in a zone of highly fractured volcanic and metamorphosed rocks of Cambrian age.2 Large reserves of lead, zinc and silver ores have been proved in these mines and are under energetic exploitation. The country-rocks are felspathic grits and rhyolitic tuffs, the felspars of which are replaced by galena. Blende and copper-pyrites are assoc­ iated with the lead-ores, together with their alteration-products in the zone of weathering—cerussite, anglesite, smithsonite, and malachite. For many years the Bawdwin lead was worked more from the heaps of slags left by the old Chinese workers of these mines than from the ores mined from deposits in situ. The annual production now reaches 74,000 tons of metallic lead, extracted from 445,000 tons of the ore mined. The Bawdwin ores belong, geologically, to the class of metasomatic replacements, the original minerals of the country-rock having been substituted chemically by the sulphides and carbonates of lead and zinc, by the process of molecular replacement. Silver—India is the largest consumer of silver in the world, the extent of its average annual imports being £10,000,000. But with the exception of the quantity of silver won from the Kolar gold-ores, aggregating on an average about 25,000 ozs., no silver is produced in 1 Coggin Brown, Bull. I. I. and L. No. 19, 1922. 2 Rec. G.S.I. vol. xxxvii. pt. 3, 1909.

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the country. The production of silver from the rich argentiferous lead­ line ores of the Bawdwin Mines of Burma, however, has shown a marked increase. The silver content of the Bawdwin lead-ores varies from 10-30 ozs. per ton of lead, and wTith the steady increase in the output of lead of late years there has been a corresponding rise in the amount of silver raised. In 1929 the figures touched 7,280,000 ozs., valued at over a crore of rupees. Zinc—A considerable amount of zinc is obtained in the mining of galena from the Bawdwin mines. The ore is blende intimately mixed with galena. The average yearly output of zinc was about 90 tons, but in the year 1923 the Quantity raised suddenly increased to 18,000 tons. In 1935 the quantity of zinc-concentrate produced at the Namtu plant was 78,000 tons, valued at over 40 lacs of rupees. I t is thought that the Bawdwin zinc deposits will prove as important as, if not more important than, the lead deposits in the near future. A workable deposit of zinc-blende of considerable purity occurring in lenticular veins and lodes has been discovered in the Riasi district of Kashmir in association with a Palaeozoic limestone. Tin Tin ore of Mergui and Tavoy—With the exception of a few isolated occurrences of cassiterite crystals in Palanpur and its occurrence in situ in the gneissic rocks of Hazaribagh, the only deposits of tin ore, of workable proportions, are those of Burma—the Mergui and Tavoy districts of Lower Burma,1 which have supplied a large quantity of tin from a remote antiquity. The most important tin ore is cassiterite, occurring in quartz-veins and pegmatites, associated with wolfram, molybdenite and some sulphides in granitic intrusions traversing an ancient schistose series of rocks (provisionally named the Mergui series), and also in pegmatitic veins intersecting both the rocks. But the greater proportion of the ore is obtained, not from the deposits in situ, but from the washing of river-gravels (stream-tin or tin-stone) and from dredging the river-beds of the tin-bearing areas, where the ore is collected by a process of natural concentration by running water. The value of the total amount of tin concentrates (roughly 6000 tons yearly) produced in Burma has of late risen to nearly Rs. one crore per year, of wiiich the larger share belongs to Tavoy.

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Wolfram Wolfram of Tavoy—Previous to 1914, Burma contributed nearly a third of the total production of wolfram of the world, but subsequently it increased its output to a much larger extent, heading the list of the world’s producers of tungsten, with 3600 tons of ore per annum. Since 1921 wolfram-mining has gone through many vicissitudes, the present yearly output of 4000 tons being regarded as a recovery. The most important and valuable occurrences of wolfram are in the Tavoy district of Lower Burma,1 where the tungsten-ore is found in the form of the mineral wolframite in a belt of granitic intrusions among a metamorphic series of rocks (Mergui series). The tin-ore, cassiterite, mentioned on the preceding page, occurs in the same group of rocks, at places associated with wolframite. Wolfram chiefly occurs in quartz-veins or lodes, associated with minerals like tourmaline, columbite, and molybdenite. From its mode of occurrence as well as from its association with the above-named minerals, it i£ clear that wolfram is of pneumatolytic origin, i.e. formed by the action of “ mineralising ” gases and vapours issuing from the granitic magma. The cassiterite has also originated in a similar manner. WTolfram is also found in India in Nagpur, Trichinopoly and Rajputana, but not in quantities sufficient to support a mining industry. Uses of tungsten—Tungsten possesses several valuable properties which-give to it its great industrial and military utility. Among these the most important is the property of “ self-hardening ”, which it imparts to steel when added to the latter. Over 95 per cent, of the wolfram mined is absorbed by the steel industry. All high-speed steel cutting-tools have a certain proportion of tungsten in them. Tung­ sten-steel is largely used in the manufacture of munitions, of armour plates, of the heavy guns, etc., which enables them to stand the heavy charge of modern explosives. Tungsten, by repeated heating, is given the property of great ductility, and hence wires of extreme fineness and great strength, suitable for electric lamps, are manufactured. The value of tungsten-ore (wolframite) was more than £80 per ton before the great rise in the industry during the war. 1 Mem. G.S.I. vol. xliv. pt. 2, 1923 ; Rec. G.S.I. vol. xliii, pt. 1, 1913 ; op cit. vol. 1. pt. 2, 1919.

1 liec. G.S.I. vols. xxxvii and xxxviii. pts. 1, 1908 and 1909, Annual R eports; Coggin Brown and A. M. Heron, Ore Deposits of Tavoy, Mem. G.S.I. vol. xliv. pt. 2, 1923. w.a.1.

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Chromium Occurrence—Chromite, the principal ore of chromium, occurs as a product of magmatic differentiation in the form of segregation masses and veins in ultra-basic, intrusive rocks, like dunites, peridotites, ser­ pentines, etc. In such form it occurs in Baluchistan, Mysore and in Singhbhum. The Baluchistan deposits are the most important and are capable of much larger output than the present yearly one of some 12.000 tons. Chromite occurs in the Quetta and Zhob districts in the serpentines associated with ultra-basic intrusions of late Cretaceous age. The Mysore and Singhbhum deposits produce respectively 14.000 and 5000 tons yearly. Some chromite occurs in the “ Chalk hills ” (magnesite-veins) near Salem, but it is not worked. Large deposits of chromite occurring in dunite intrusions forming mountainmasses have been discovered by the Mineral Survey of Kashmir in the Dras valley of Ladakh, Kashmir. Uses—Chromite is used in the manufacture of refractory bricks for furnace-linings. Its further use lies in its being the raw material of chromium. An alloy of chromium and iron (ferro-chrome) is used in the making of rustless and stainless steels and armour-plates. A large amount of chromium is used in the manufacture of mordants and pigments, because of the red, yellow and green colours of its salts. In all the above occurrences chromite is a primary ore of magmatic origin. Other Metals Ores of the following metals also occur in India, but their deposits ar*i of very limited proportions and are not at the present day of any considerable economic value : Antimony—Sulphide of antimony, stibnite, is found in deposits of considerable size a t the end of the Shigri glacier in the province of Lahoul, but the lodes are inaccessible. I t occurs mixed with galena and blende in the granitoid gneiss of that area. Stibnite is also found in Vizagapatam and in Hazaribagh. But the production of stibnite from these bodies is variable, and there does not appear to be any commercial possibility for them unless metallic antimony is extracted on the spot. Arsenic—Sulphides of arsenic, orpiment and realgar, form large de­ posits in Chitral on the North-West Frontier and in Kumaon. The orpiment-mines of the first locality are well known for the beautifully foliated masses of pure orpiment occurring in them, and form the chief

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indigenous source, but the output has fallen off considerably of late years. The orpiment occurs in calcareous shales and marble in close proximity to a dyke of basic intrusive rock. The chief use of orpiment is as a pigment in lacquer-work ; it is also employed in pyrotechnics because of its burning with a dazzling bluish-white light.1 Arsenopyrite occurs near Darjeeling and in the Bhutna valley, Kashmir. Cobalt and nickel—Cobalt and Nickel-ores are not among the eco­ nomic products of India. A few crystals of the sulphide of both these metals are found in the famous copper-mines of Khetri, Jaipur, Rajputana. The Sehta of the Indian jewellers is the sulphide of cobalt, which is used for the making of blue enamel. Nickeliferous pyrrhotite and chalcopyrite occur at some places in South India, e.g. in the auriferous quartz-reefs of Kolar, in Travancore, etc., but the occur­ rences are not of sufficient magnitude to support mining operations. Small deposits of nickeliferous pyrites, containing 1*7 per cent, of Ni have been found in the Purana rocks of Ramsu and Buniyar and in the Carboniferous limestone (Great limestone) of Riasi, Kashmir. Zinc—Besides the ore associated with the lead-ores of Bawdwin (p. 352), some zinc occurs with the antimony deposits of Shigri, and the copper-deposits of Sikkim. Smithsonite is found at Udaipur in Rajputana and a few other places. Lodes of zinc-ore, blende, occur in the Riasi district, Kashmir in Carboniferous limestones. The veins are lenticular, swelling to nests of over 500 cubic feet. Some thousand tons of blende masses occur as float ore on the surface. v ^7. PRECIOUS AND SEMI-PRECIOUS STONES2 Diamonds Panna and Golconda diamonds—In ancient times India had ac­ quired great fame as a source of diamonds, all the celebrated stones of antiquity being the produce of its mines, but the reputation has died out since the discovery of the diamond-mines of Brazil and the Trans­ vaal, and at the present time the production has fallen to a few stones annually of but indifferent value. Even so late as the times of the Emperor Akbar, diamond-mining was a flourishing industry, for the field of Panna alone is stated to have fetched to his Government an annual royalty of 12 lacs of rupees. The localities noted in history as 1 Coggin Brown, Bulletin of I. K and L. No. 6, 1921. 2 Goodchild, Precious Stones (Constable).

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the great diamond centres were Bundelkhand (for “ Panna dia­ monds ”); the districts of Kurnool, Cuddapah, Bellary, etc., in the Madras Presidency (for the “ Golconda diamonds ”) ; and some places in Central India such as Sambalpur, Chanda, etc. The diamondiferous strata in all cases belong to the Vindhyan system of deposits. A certain proportion of diamonds were also obtained from the surfacediggings and alluvial-gravels of the rivers of these districts. Two diamond-bearing horizons occur among the Upper Vindhyan rocks of Central India : one of these (Panna State) is a thin conglomerate-band separating the Kaimur sandstone from the Rewah series, and the other, also a conglomerate, lies between the latter and the Bhander series. The diamonds are not indigenous to the Vindhyan rocks but have been assembled as rolled pebbles, like the other pebbles of these conglo­ merates, all derived from the older rocks. The original matrix of the gem from which it separated out by crystallisation, is not known with certainty. Probably it lies in the dykes of basic volcanic rocks assoc­ ia te d with the Bijawar series.1 The most famous diamonds of India jfrom the above-noted localities are : the “ Koh-i-noor ”, 186 carats ; | the “ Great Mogul ”, 280 carats ; the “ Orloff ”, 193 carats ; the [ “ P itt ”, 410 c a ra ts; the value of the last-named stone, re-cut to ? 136f carats, is estimated at £480,000.

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detritus. The output of the Burma ruby-mines amounted, some years a^o, to over £95,000 annually, but it has declined of late years.1 The average annual royalty of Rs. 1,70,000 indicates the state of the in­ dustry at the present day. Sapphires of Kashmir—The Burma ruby area also yields sapphires occasionally, a sapphire weighing 1000 carats was found in 1929 and another of 630 carats in 1930 from Mogok, but a larger source of sapphires in India was up till lately Kashmir. The gem was first dis­ covered in Kashmir in 1882 ; it there occurs as an original constituent of a fine-grained highly felspathic gneiss at Padar in the Kishtwar district of the Zanskar range, at a high elevation. Transparent crystallised corundum occurs in pegmatite veins cutting actinoliteschist lenticles in Salkhala marble, at an altitude of 15,000 feet. Associated minerals in the pegmatite are prehnite, tourmaline, beryl, spodumene and lazulite. Sapphires were also obtained from the talusdebris at the foot of the hill-slopes. Stones of perfect lustre and of high degree of purity have been obtained from this locality in the earlier years, but the larger and more perfect crystals, of value as gems, appeared to have become exhausted since 1908 ; late discovery, however, by the Mineral Survey of Kashmir has revealed a large quantity of crystallised transparent corundum. The bulk of the out- * put from the mines is confined to what are called “ rock-sapphires ”, valueless for gems and of use as abrasives, watch jewels, etc.

^ Rubies and Sapphires (Corundum)2 Burma rubies—Crystallised and transparent varieties of corundum, when of a beautiful red colour, form the highly valued jewel ruby, and, when of a light blue tint, the gem sapphire. Rubies of deep carminered colour, “ the colour of pigeons’ blood ”, and perfect lustre are often of greater value than diamonds. Rubies are mined at the Mogok district (Ruby Mines district) of Upper Burma, north of Mandalay, which has been a celebrated locality of this gem for a long time. The best rubies of the world come from this district from, an area covering some 25 to 30 sq. miles, of which Mogok is the centre. The matrix of the ruby is a crystalline limestone—ruby limestone (see p. 60)—associated with and forming an integral part of the sur­ rounding gneisses and schists. The rubies are found in situ in the limestone along with a number of other secondary minerals occurring in it. Some stones are also obtained from the hill-wash and alluvial 1Vredenburg, Rec. O.S.I. vol. xxxiii. pt. 4, 1906 ; K. P. Sinor, The Panna Diamondfield, Bombay, i932. 8 T. H. Holland, Corundum, G.S.I., 1898.

Spinel Spinel when of sufficient transparency and good colour is used in jewellery ; it constitutes the gem ballas-ruby when of rose-red colour and spinel-ruby when of a deeper red. Rubicelli is the name given to an orange-red variety. Spinel-rubies occur in th e Burmese area assoc­ iated with true rubies; also to some extent in Ceylon, in the wellknown gem-sands of Ceylon, along with many other semi-precious and ornamental stones. Jadeite Jade is a highly-valued ornamental stone on account of its great toughness, colour and the high lustrous polish it takes ; it is especially valued in China, to which country almost the whole Indian output is exported. A large number of mineral compounds pass under the name 1 One ruby from the Mogok mines, 38£ carats in weight, was sold for £20,000 in London in 1875.

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of jade, but the true mineral, also named nephrite, so much sought after, is a comparatively rare substance. Its occurrence is not known in India, but a mineral very much similar to it in many of its qualities and known as jadeite, is largely quarried in Burma. True jade comes into India from the Karakash valley of South Turkestan. y Occurrence. Formation—The stones are of various shades of green, violet, orange, red, blue, or milk-white colour, and even black. Jade belongs to the group of amphiboles, being allied mineralogically to the species tremolite, while jadeite, resembling the latter in many of its physical characters, is more allied to the pyroxene group, being a species of spodumene. The occurrence of the latter mineral in India is principally confined to the Miocene rocks of'Upper Burma (Myitkyina district), where its extraction and export is a long-established and remunerative industry. I t occurs either as boulders in the alluvial gravels or as an alteration-product in the large serpentinous intrusions in the district of Tawmaw.1 The formation of jade in serpentine is regarded by some as due to magmatic segregation 2 tak­ ing place in the basic igneous intrusions of Miocene age. By others its presence is attributed to the effects of contact metamorphism on a dyke of nepheline-albite rock traversing masses of serpentine. In the period of its greatest prosperity, the jade industry was a flourishing trade in Burma, but at present it has considerably lessened, which is to some extent due to the inferior quality of the jadestone obtained. In 1932 Burma exported 3000 cwts. of jadestone of the aggregate value of Rs. 3,26,000. Sang-e-Yeshm, regarded as jade in the Punjab, is only a variety of serpentine. I t differs from the original mineral in all its characters, being not so tough, much softer and incapable of receiving the ex­ quisite polish of jade.

from both of which localities stones of considerable value were once obtained. Recently a new and highly productive locality for aqua­ marines has been discovered in the Kashmir State in the Shigar valley in Skardu, whence crystals of considerable .size and purity are recovered. The gem occurs in coarse pegmatite veins traversing biotite-gneiss. Common beryl occurs in very large crystals, sometimes a foot in length, in the granite-pegmatite of many parts of India, but only rarely do they include some transparent fragments of the required purity.

V Beryl Emeralds and aquamarines—Beryl when transparent and of per­ fect colour and lustre is a highly valued gem. Its colour varies much from colourless to shades of green, blue or even yellow. The muchprized green variety is the emerald, while the blue is distinguished as aquamarine. Emeralds are rare in India. Aquamarines suitable for use as gems are obtained from pegmatite-veins crossing the Archaean gneiss at some places in Bihar and Nellore. Good aquamarines also occur in the Coimbatore district and in Kishengarh (Rajputana), 1Bleeck Rec. G.S.I. vol. xxxvi. pt. 4, 1908. 2H. L. Chhibber.

Chrysoberyl Chrysoberyl is a stone of different composition from beryl. It is of greenish-white to olive-green colour. A few good stones in the form of platy crystals of tabular habit are obtained from pegmatite-veins in Kishengarh in Rajputana, which also yield mica and aquamarines. They are found in some felspar-veins in the nepheline-syenites of Coimbatore. Usually they are too much flawed and cracked to be suitable for cutting as gems. Chrysoberyl crystals when possessing Alexandrite is the deep a chatoyant lustre are known as “ Cat’s eyes emerald-green variety found in Ceylon. */Garnets Garnet as a gem-stone—Garnet possesses some of the requisites of a gem-stone—a high refractive index and lustre, a great hardness, a pleasing colour, transparency, etc.—and would be appreciated as such, were it but put on the market in restricted quantitites. Garnets are most abundant in the metamorphosed rocks of Rajputana and Ceylon, especially in the mica-schists, and large transparent crystals are fre­ quently found. Quantities of garnets are exported to foreign coun­ tries for use in cheap jewellery. The variety used for this purpose is almandine, of crimson to red and violet colours. Crystals of large size, derived from Purana mica-schist, are worked at Jaipur, Delhi and at Kishengarh, where they are cut into various shapes for gems. Those of Kishengarh are considered to be the finest in India, and support a regular industry of aboUt a lac of rupees yearly. Zircon Zircons occur in various parts of India, but nowhere quite flawless or with the degree of transparency required in a gem. Hyacinth (the transparent red variety) is found at Kedar Nath on the Ganges.

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Tourmalines Red and green tourmalines—Pellucid and beautifully coloured varieties of tourmaline, red, green or blue, are worked as gems. The finQ red transparent variety Rubellite is obtained from the ruby-mines district of Burma, where it occurs in decomposed granite veins. The green variety known as Indicolite occurs in Hazaribagh (Bengal) and in the Padar district of Kashmir, where also some transparent crystals of rubellite are found. The latter tourmalines possess greater trans­ parency, but are much fissured. Gem-tourmalines are also obtained from Ceylon from the noted gem-sands or gravels of that island. Other gem-stones of India Besides the above-named varieties, other crystallised minerals, when of fine colour and attractive appearance and possessing some of the other qualities of gems, e.g. hardness, transparency, etc., are cut for ornamental purposes in different parts of the country. Among such minerals are the pleochroic mineral iolite or cordierite of Ceylon ; kyanites or cyanites found at Narnaul in the Patiala State ; rhodonite (pink manganese silicate) of some parts of the Central Provinces apatite (a sea-green variety) met with in the kodurites of Yizagaipatam. Moonstone and amazon-stone are ornamental varieties [of felspar, the former a pearly opalescent orthoclase, met with fin Ceylon, and the latter a green microcline occurring in Kashmir and elsewhere. Gem-cutting is a regular industry in places like Delhi, Jaipur and Ceylon. Agates Various forms of chalcedonic silica, agates, carnelian, blood-stone, onyx, jasper, etc., are known under the general name of akik (agate) in India. The principal material of these semi-precious sTones is ob­ tained from the amygdaloidal basalts of the Deccan, where various kinds of chalcedonic silica have filled up, by infiltration, the steamholes or cavities of the lavas. The chief place which supplies raw akik is Ratanpur in the Rajpipla State, where rolled pebbles of these amygdules are contained in a Tertiary conglomerate. On mining, the stones are first baked in earthen pots, which process intensifies the colouring of the bands in the agates. The cutting and polishing is done by the lapidaries of Cambay, who fashion out of them (after a

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most wasteful process of chipping), a number of beautiful but small articles and ornaments. The annual output at Ratanpur is about 100 tons. Cambay used to be a large market of Indian agates in past years for different parts of the world. Rock Crystal Rock-crystal, or crystallised, transparent, quartz, is also cut for ornamental objects, such as cheap jewels (vallum diamonds), cups, handles, etc. The chief places are Tanjor, Kashmir, Kalabagh, etc., from whence crystalline quartz of requisite purity and transparency is obtained. Amethyst and Rose-Quartz, the purple and pink-coloured varieties of rock-crystal are cut as ornamental stones and gem-stones. Amethyst occurs in some geodes in Deccan Trap, filling up lava-cavities, near Jabalpur; it also occurs in Bashar State, Punjab. Rose quartz is found in Chhindwara and Warangal, C.P. Amber Amber is mineral resin, i.e. the fossilised gum of extinct coniferous trees. It is extracted by means of pits from some Miocene clay-beds in the Hukawng valley of North Burma. A few cwts. are produced annually, from 50 to 200, with an average value of 90 to 100 rupees per cwt. I t occurs in round fragments and lumps, transparent or translucent, often crowded with inclusions and with veins of calcite. Amber is employed in medicine, in the arts, for jewellery, etc., and is highly prized when of a transparent or translucent nature.

f

8. ECONOMIC MINERALS AND MINERAL PRODUCTS

Here we shall consider the remaining economic mineral products, mostly non-metallic minerals of direct utility or of application in the various modern industries and arts. They include salts and saline substances, raw materials for a number of manufactures, and sub­ stances- of economic value such as abrasives, soil-fertilisers, the rare minerals, etc. With regard to their geological occurrence, some are found as constituents, original or secondary, of the igneous rocks; some as beds or lenticles among the stratified rocks, formed by chemical agencies; while others occur as vein-stones or ganguematerials occurring in association with mineral-veins or lodes or

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filling up pockets or cavities in the rocks. these products are : 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13.

Salt. Saltpetre. Alum. Borax. Reh. Mica. Corundum. Kyanite and Sillimanite. Beryl. Monazite. Graphite. Steatite. Gypsum. Salt

The more important of 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.

Magnesite. Asbestos. Barytes. Fluor-spar. Phosphatic Rocks. Mineral Paints. Uranium. Titanium. Vanadium. Rare Minerals. Pyrite. Sulphur.

Sources of salt. Sea-water. Brine-wells—There are three sources of production of this useful material in India : (1) sea-water, along the coasts of the Peninsula; (2) brine-springs, wells and salt-lakes of some arid tracts, as of Rajputana and the United Provinces ; (3) rock-salt deposits contained in Cutch, Mandi State, the Salt-Range and in the Kohat region. The average annual production of salt from these, sources is a little over I f million tons, the whole of which is consumed in the country. The first is the most productive and an everlasting source, contributing more than 80 per cent, of the salt consumed in India. The manufacture is carried on at some places along the coasts of Bombay and Madras, the process being mere solar evaporation of the sea-water enclosed in artificial pools or natural lagoons. A solid pan of salt results, which is afterwards refined by recrystallisation. Concentration from brine springs and wells is carried on in various parts of the United Provinces, Bihar, Delhi, Agra, the delta of the Indus, Cutch and in Rajputana. The principal sources of salt in the last-named province are the salt-lakes of Sambhar in Jaipur, Dindwana and Phalodi in Jodhpur, and Lonkara-Sur in Bikaner. The salinity of the lakes in this area of internal drainage was for long a matter of conjecture, but the investigations of Holland and Christie 1 have conclusively shown that the salt is brought as fine dust by the south-west monsoon from the Rann of Cutch and from the sea1 Rec. G.S.I. vol. xxxviii pt. 2, 1909.

3G3

coasts, and is dropped in the interior of Rajputana when the velocity of the winds passing over it has decreased. Rock-salt mines—The rock-salt deposits of Northern India also constitute an immense source of pure crystallised sodium chloride. At Khewra, in the Jhelum district, two beds of rock-salt 550 feet thick are worked ; they contain five seams of pure salt totalling 275 feet intercalated with only a few earthy or impure layers unfit for direct consumption. The horizontal extension of these beds or lenticles is not known definitely, but it is thought to be great. Smaller salt-mines are situated at some other parts along these mountains. A salt-deposit of even greater vertical extent than that worked at Khewra is laid bare by the denudation of an anticline in the Kohat district, lying north of the Salt-Range. Here the salt is taken out by open quarrying in the salt-beds a t the centre of the anticline near Bahadur Khel. The thickness of the beds is 1000 feet and their lateral extent 8 miles. The salt is nearly pure crystallised sodium chloride, with a distinct greyish tint owing to slight bituminous admixture. Salt-beds of considerable size occur in the Mandi State, while some million tons of pure rocksalt, produced by evaporation of sea-water in enclosed basins, occurs embedded in the sands of the Rann of Cutch and in the alluvial tract south-east of Sind. The average annual amount of rock-salt extracted from the mines in the Salt-Range, Kohat and Mandi State, is about 170,000 tons. Other Salts—The Salt-Range deposits contain, beside sodium chloride, some salts of magnesium and potassium. The latter salts are of importance for their use in agriculture and some industries. Numerous seams of potash-bearing minerals (containing a potassium percentage from 6 to 14 per cent.), such as sylvite, lcainite, langbeinite, etc., have been found, generally underlying the layers of red earthy salt (Icalar).1 Carbonate—Carbonate and sulphate of soda were formerly derived from the Reh efflorescences of the alluvial plains of Northern India. The extent of these accumulations may be judged from an estimate of the quantity of sodium carbonate available, viz. several million tons per annum, from the Reh efflorescences in the soils of United Pro­ vinces.2 Carbonate of soda forms a large ingredient of the salt-water of the Lonar lake, in Buldana district, from which it was formerly extracted for commerce. The Lonar lake is estimated to contain 1 Rec. G.S.I. vol. xliv. pt. 4, 1914. 2 E. R. Watson and K. C. Mukerji, Joum . I. I. and L. vol. ii, 1922.

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about 7000 tons of alkaline salts. But the cheap supply of chemically manufactured soda prohibits any industrial working of these salts now-.1 The Dhands, or alkaline lakes (p. 290), of eastern Sind are another source of sodium salts, carbonate, chloride, and sulphate. The pro­ duction of crude sodium carbonate and bi-carbonate in 1934 was about 2000 tons.2 Saltpetre or Nitre (Potassium Nitrate)3 India, principally the province of Bihar, used to export this com­ pound in very large amounts before the introduction of artificially manufactured nitrate, and constituted the most important source of supply to Europe and the United States of America. Mode of occurrence of nitre—Saltpetre is a natural product formed in the soil of the alluvial districts by natural processes under the peculiar conditions of climate prevailing in those districts. The thickly populated agricultural province of Bihar, with its alternately warm and humid climate, offers the most favourable conditions for the accumulation of this salt in the sub-soil. The large quantities of animal and vegetable refuse gathered round the agricultural villages of Bihar are decomposed into ammonia and other nitrogenous sub­ stances ; these are acted upon by certain kinds of bacteria (nitrifying bacteria) in the damp hot weather, with the result that a t first nitrous and then nitric acid is produced in the soil. This nitric acid readily acts upon the salts of potassium with which the soil of the villages is impregnated on account of the large quantities of wood and dung ashes constantly being heaped by villagers around their habitations. The nitrate of potassium thus produced is dissolved by rain-water and accumulated in the sub-soil, from which the salt re-ascends to the sur­ face by capillary action in the period of desiccation following the rainy weather. Large quantities of nitre are thus left as a saline efflorescence on the surface of the soil along with some other salts, such as chloride of sodium and carbonate of sodium. Its production—The efflorescence is collected from the soil, lixiviated and evaporated, and the nitre separated by fractional crystallisation. It is then sent to the refineries for further purification. In past years 1 Rec. G.S.I. vol. xii. pt. 4, 1912. 2 Mem. G.S.I. vol. xlvii. pt. 2, 1923. * Hutchinson, Saltpetre, its Origin and Extraction in India, Bulletin 68 (1917), Agricultural Department of India.

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Bihar alone used to produce more than 20,000 tons of nitre per year. The present aggregate export of refined nitre from Bihar, Punjab, Sind and other parts of India hardly amounts to 10,000 tons. Uses—The chief use for nitre or saltpetre was in the manufacture of gunpowder and explosives before the discoveries of modern chem­ istry brought into use other compounds for these purposes. Nitre is employed in the manufacture of sulphuric acid and as an oxidiser in numerous chemical processes. A subordinate use of nitre is as manure for the soil. Alum Alums are not natural but secondary products manufactured out of pyritous shales or “ alum shales [Production—Pyritous shales when exposed to the air, under heat and moisture, give rise to the oxidation of the pyrites, producing iron sulphate and free sulphuric acid. The latter attacks the alumina of the shales and converts it into aluminium sulphate. On the addition of potash-salts, such as nitre or common wood-ashes, potash-alum is produced, and when common salt or other soda-salts are introduced, soda-alum is produced. In this way several alums are made, depending upon the base added. The natural weathering of the shales being a very slow process, it is expedited in the artificial production of alum by roasting it. The roasted shale is then lixiviated and concentrated. A mixture of various soda and potash-salts is then added and the alum allowed to crystallise out.] The most common alums produced in India are soda and potash alums. There w^as a flourishing alum industry in the past in Cutch, Rajputana and parts of the Punjab. But it is no longer remunerative in face of the cheap chemical manufactured alums, and is carried on only at two localities, Kalabagh1 and Cutch. The principal use of the alum manufactured in India is in the dyeing and tanning industries. Soluble sulphates of iron and copper—copperas and blue-vitriol— are obtained as bye-products in the manufacture of alums from pyritous shales. Borax Borax from Tibet—Borax occurs as a precipitate from the hot springs of the Puga valley, Ladakh, which occur in association with some sulphur deposits. Borax is an ingredient of many of the saltlakes of Tibet, along with the other salts of sodium. The borax of the Tibetan lakes is obtained either by means of diggings, on the shores of 1 Rec. G.S.I. vol. xl. pt. 4, 1910.

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the lakes, or by the evaporation of their waters. The original source of the borax in these lakes is thought to be the hot springs, like those of Puga mentioned on the preceding page. Like nitre, alum and similar products, the borax trade, which was formerly a large and remunerative one, has seriously declined owing to the discovery of deposits of calcium borate in America, from which the compound is now synthetically prepared. The industry consisted of the importation of partly refined borax into the Punjab and United Provinces, from Ladakh and Tibet, and its exportation to foreign countries. About 16,000 cwts. were thus exported yearly, valued at Rs. 360,000, whereas now it is only about 1000 cwts. Borax is of use in the manufacture of superior grades of glass, artificial gems, soaps, varnishes and in soldering and enamelling.

lands into cultivable soils by the removal of these salts would add millions of acres to the agricultural area of India and bring back under cultivation what are now altogether sterile uninhabited districts. The carbonate and sulphate of soda, the chief constituents of Reh, were formerly of some use as a source of salts of alkalies, and were pro­ duced in some quantity for local industry, but their production is no longer remunerative. (See p. 363)

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Reh or Kallar The origin of reh salts—R&h or Kallar is a vernacular name of a saline efflorescence composed of a mixture of sodium carbonate, suli phate and chloride, together with varying proportions of calcium and magnesium salts found on the surface of alluvial soils in the drier districts of the Gangetic plains. Reh is not an economic product, but it is described here because of its negative virtues as such. Some soils are so much impregnated with these salts th at they are rendered quite unfit for cultivation. Large tracts of the country, particularly the northern parts of United Provinces, Punjab and Rajputana, once fertile and populous, are through its agency thrown out of cultivation and made quite desolate. The cause of this impregnation of the salts in the soil and sub-soil is this : The rivers draining the mountains carry with them a certain proportion of chemically dissolved matter, besides that held in mechanical suspension, in their waters. The salts so carried are chiefly the carbonates of calcium and magnesium and their sulphates, together with some quantity of sodium chloride, etc. In the plains-track of the rivers, these salts find their way, by percola­ tion, into the sub-soil, saturating it up to a certain level. In many parts of the hot alluvial plains, which have got no underground drainage of water, the salts go on accumulating and in course of time become concentrated, forming new combinations by interaction be­ tween previously existing salts. Rain water, percolating downwards, dissolves the more soluble of these salts and brings them back to the surface during the summer months by capillary action, where they form a white efflorescent crust. The reclaiming of these barren kallar

Mica Uses of Mica—Mica (muscovite) finds increased uses in many in­ dustries, and is a valuable article of trade. The chief use is as an in­ sulating material in electric goods ; another is as a substitute for glass in glazing and many other purposes. For the latter purpose, however, \ only large transparent sheets are suitable. Formerly an enormous amount of what is called scrajp-mica (small pieces of flakes of mica), t the waste of mica-mines and quarries, was considered valueless and was Jhrown away. A use has now been found for this substance in the making of micanite—mica-boards—by cementing small bits of scrap mica under pressure. Micanite is now employed for many pur­ poses in which sheet mica was formerly used. Scrap mica is also ground for making paints, lubricants, etc. ^ T h e mica-deposits of the Indian peninsula are considered to be the finest in the world, because of the large size and perfection of the crystal plates obtainable at several places. This quality of the mica is due to the immunity from all disturbances such as crumpling, shear­ ing, etc., of the parent rocks. Crystals more than three yards in dia­ meter are obtained occasionally from the Nellore mines, from coarse pegmatite veins traversing Archaean schists and gneisses, from which valuable flawless sheets of great thinness and transparency are cloven off. Mica-deposits of Nellore and Hazaribagh—India is the largest pro­ ducer of mica in the world, contributing, of late years, more than 170,000 cwts. per year, bringing in a return of Rs. 90,00,000. The whole output of the mines is exported, there being no indigenous in­ dustry to absorb any part of the product, or for the manufacture of micanite. Although muscovite is a most widely distributed mineral in the crystalline rocks of India, marketable mica is restricted to a few jpegmatite-veins only, carrying large perfect crystals, free from wrinkling or foreign inclusions. These pegmatite veins cross the Archaean and Dharwar crystalline rocks, granites, gneisses and

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schists, but they become the carriers of good mica only when they cut through mica-schists. The principal mica-mining centres in India are the Hazaribagh, Gaya and Monghyr districts of Bihar, the Nellore district of Madras, and Ajmere and Merwara in Rajputana. Of these Bihar is the largest producer, while Rajputana contributes only 4 per cent, of the total.1 The dark-coloured micas, biotite, phlogopite, etc., have no commercial use. Lepidolite, lithia mica, the source of lithium oxide, occurs in pegmatite veins and lenses of 30 ft. width and 300 to 400 yards length in the Bastar State of the Central Provinces, containing over 3 per cent, of lithium oxide. The mineral is of use in the glass and porcelain industries. Corundum2 Occurrence. Distribution—Corundum is an original constituent of a number of igneous rocks of acid or basic composition whether plutonic or volcanic. I t generally occurs in'masses, crystals, or irregular grains in pegmatites, granites, diorites, basalts, peridotites, etc. The presence of corundum under such conditions is regarded as due to an excess of the base A120 3 in the original magma, over and above its proper proportion to form the usual varieties of aluminous silicates.3 India possesses large resources in this useful mineral, which are, for the most part, concentrated in Mysore and Madras. Other localities are Singhbhum ; Rewah (Pipra), where a bed of corundum 800 yards long, 70 yards wide and 30 feet thick is found ; the Mogok district (Ruby Mines district), in Upper Burma ; Assam (Khasi hills); some parts of Bihar ; the Zanskar range in Kashmir, etc. In Burma the famous ruby-limestone contains a notable quantity of corundum as an essential constituent of the rock, some of which has crystallised into the transparent varieties of the mineral, ruby and sapphire. In Madras there is a large area of corundiferous rocks covering some parts of Trichinopoly, Nellore, Salem and Coimbatore. Mostly the corun­ dum occurs in situ in the coarse-grained gneisses, in small round grains or in large crystals measuring some inches in size. I t also forms a constituent of the eleaolite-syenites of Sivamalai and of the coarse felspar-rock of Coimbatore. 1 Mica Deposits of India, Mem. G.S.I. vol. xxxiv. pt. 2, 1902; Bull, of I. I. and L. No. 15. 2 T. H. Holland, Corundum, G.S.I., 1898. 3 In the above instances corundum occurs as an original constituent of the magma, but the mineral also occurs in many cases as a secondary product in the zones of contact-metamorphism around plutonic intrusions.

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Uses—The chief use of corundum is as an abrasive material because of its great hardness. Emery is an impure variety of corundum, mixed with iron-ores and adulterated with spinel, garnet, etc. The abrading power of emery is much less than th at of corundum, while th at of corundum again is far below that of the crystallised variety sapphire. As an abrasive corundum has now many rivals, in such artificial pro­ ducts as carborundum, alundum, etc. Corundum is used in the form of hones, wheels, powder, etc., by the lapidaries for cutting and polishing gems, glass, etc. The total annual production in India averages about 6000 to 7000 cwts., valued at about Rs. 30,000. Other abrasives. Millstones—While dealing with abrasives, we might also consider here materials suitable for millstones and grind­ stones that are raised in India. A number of varieties of stones are quarried for cutting into millstones, though rocks that are the most suitable for this purpose are hard, coarse grits or quartzites. There is a scarcity of such rocks in most parts of the country and hence the stones commonly resorted to are granites, hard gritty Vindhyan sand­ stones and Gondwana grits and sandstones, chiefly of the Barakar stage. Grindstones—Grindstones, or honestones, are cut from any homo­ geneous close-grained rocks belonging to one or the other of the following varieties : fine sandstones, lydite, novaculite, hornstone, fine-grained lava, slate, etc. v " ' Kyanite and SiUimanite These aluminous silicates, owing to their possessing certain valu­ able properties as refractories at high temperatures, especially in the manufacture of ceramics, have come into prominence of late years. India possesses considerable resources in both these minerals and can meet the demands of European and American markets for a long time. Kyanite occurs mainly in Singhbhum as kyanite-quartz rock and as massive kyanite-rock in beds of enormous size in the Archaean schists ; sillimanite occurs also in the same rock-system in the Rewah State (Pipra village) and in the Khasi plateau of Assam. Corundum occurs with these in close relationship, forming a group of highly aluminous schists and gneisses. A high degree of purity, with percentage of aluminum silicate reaching 95 to 97, characterises both these minerals from Rewah, Assam and Singhbhum. The present day exports of kyanite are about 24,000 tons, value Rs. 350,000.1 1 J . A. Dunn, Mem. G.S.I. vol. lii. pt. 2, 1929 ; and Mem. G.S.I. vol. lxix, 1937. w.o.l. 2a

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Beryl

It forms an essential constituent of the rock known as khondalite of Orissa, a quartz-sillimanite-garnet-graphite schist. But the majority of these deposits are not of workable dimensions. Graphite occurring under such conditions is undoubtedly of igneous origin, i.e. a primitive constituent of the magma. Graphite resulting from the metamorph­ ism of carbonaceous strata, and representing the last stage of the mineralisation of vegetable matter, is practically unknown in India, except locally in the highly crushed Gondwana beds of the outer Himalayas. The largest deposits of graphite are in Ceylon, which has in the past supplied large quantities of this mineral to the world, its yearly contribution being nearly a third of the world’s total annual produce. The graphite here occurs as filling veins in the granulites and allied gneisses belonging to the Charnockite series. The struc­ ture of the veins is often columnar, the columns lying transversely to the veins. Travancore until lately was another important centre for graphite-mining, deriving the mineral from the Charnockite series of gneisses, supplying annually about 13,000 tons of the mineral (valued at Rs. 780,000). The graphite industry has practically ceased in Tra­ vancore of late years owing to the increasing depths to which mining operations have become necessary. A few other localities have been discovered among the ancient crystalline rocks, where graphite occurs, viz. Merwara in Raj­ putana, Sikkim, Coorg, Yizagapatam and in the Ruby Mines district of Upper Burma, but the quantity available is not large. Rajputana produced nearly a thousand tons in 1916 of a rather low grade. Uses—The uses of graphite lie in its refractoriness and in its high heat conductivity. For this purpose it is largely employed in the manufacture of crucibles. Its other uses are for pencil manufacture, as a lubricant, in electrotyping, etc.

Beryl occurs in the mica-pegmatite of Bihar, Ncllore, and Rajputana. Jaipur and Ajmer-Merwara contain some workable deposits of this mineral from which large crystals up to two feet in diameter are sometimes obtained. The industrial use of Beryl lies in the 12 per cent, or so of BeO employed in the manufacture of copper-beryllium alloy. The Rajputana mines exported about 300 tons in 1933 ; value Rs. 7,200. Monazite

J

Monazite is a phosphate of the rare earths—cerium, lanthanum and didymium—but its economic value depends upon a small per­ centage of thorium oxide, which it contains as an impurity. Monazite was discovered some years ago in the Travancore State in riverdetritus and along a long stretch of the coast from Cape Comorin to Quilon. At some places the monazite-sands have been concentrated by the action of the sea-waves into rich pockets. Besides monazite, the other constituents of the sand are magnetite, ilmenite, garnets, etc. ; those with a high proportion of monazite have a density of 5*5 with a light yellow colour. , Monazite of Travancore . 1 Its occurrence— The monazite of Travan­ core is derived from the pegmatite-veins crossing the charnockites of fche district. Its original formation is ascribed to pneumatolytic agencies during the later period of consolidation of the charnockite magma. It is also a small accessory constituent of the main rock. The percentage of thoria, yielded by the Travancore monazite, on which the commercial value of the mineral depends, is variable from 8 to 10 per cent. In 1918 India exported concentrated monazite sands of the value of £58,000 (2100 tons). The present output is of much reduced dimensions. Uses—The industrial use of monazite lies in the incandescent pro­ perties of thoria and the other oxides of the rare earths which it con­ tains. These substances are used in the manufacture of mantles and filaments for incandescent lamps. Graphite Occurrence—Graphite occurs in small quantities in the crystalline and metamorphic rocks of various parts of the Peninsula, in pegmatite and other veins, and as lenticular masses in some schists and gneisses. 1 Tipper,

Rec. O.S.I. vol. xliv. pt. 3, 1914.

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Steatite Mode of origin of steatite—Massive, more or less impure, talc is put to a number of minor uses. From its smooth, uniform texture and soapy feel, it is called soapstone. I t is also known as pot-stone from its being carved into plates, bowls, pots, etc. Steatite is of wide occur­ rence in India, forming large masses in the Archaean and Dharwar rocks of the Peninsula and Burma ; workable deposits occur in Behar, Jabalpur, Salem, Idar and Jaipur (Rajputana) and Minbu (in Burma). The Rajputana deposits carry the mineral in thick lenticular

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beds of wide extent in the schists. Some of these beds persist for miles. At most of these places steatite is quarried in small quantities for commercial purposes. In its geological relations, steatite is often associated with dolomite (as in Jabalpur) and other magnesian rocks, and it is probable that it is derived from these rocks by metamorphic processes resulting in the conversion of the magnesium carbonate into the hydrated silicate. In other cases it is the final product of the alteration of ultra-basic and basic eruptive rocks. At Jabalpur and other places it is carved into bowls, plates and vases ; it is also used in soap-making, in pencils, in the paper industry, and as a refractory sub­ stance in making jets for gas-burners. The substance has also of late come into use as a special type of refractory, resistant to corrosive slags and as a paint of high quality for protecting steel. The annual production a t present is about 8500 tons of the value of about Rs. 2 lacs. Gypsum Gypsum forms large bedded masses or aggregates occurring in assoc­ iation with rocks of a number of different geological formations. It has not found many uses in India, as is shown by the extremely low price of the product, Re. 1 for about 15 cwt. in some of the localities where it is quarried. Large deposits of gypsum occur in the SaltRange and Kohat in association with rock-salt deposits, and in the Tertiary clays and shales of Sind and Cutch. In Jodhpur and Bikaner beds of gypsum are found among the silts of old lacustrine deposits and are of considerable economic interest locally. Millions of tons of gypsum, the alteration-product of pyritous limestone of Salkhala age, are laid bare in the mountains of the Uri district of Kashmir in a stretch of about 25 miles along the strike of the country-rocks. In Spiti the gypsum occurs in immense masses replacing Carboniferous limestones. In some cases gypsum occurs as transparent crystals (selenite) assoc­ iated with clays. The handsome massive and granular variety, known as alabaster, is used in Europe for statuary, while the silky fibrous variety, known as satin-spar, is employed in making small ornamental articles. The industrial use of gypsum is in burning it for making plaster-ofParis. In America it is increasingly used for fire-proofing wall-boards. I t is also used as a surface-dressing for lands in agriculture, and as a fertiliser, with considerable benefit to certain crops.

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Magnesite1 Mode of occurrence of magnesite—Large deposits of magnesite occur in the district of Salem as veins associated with other magnesian rocks such as dolomite, serpentines, etc. The magnesite is believed to be an alteration-product of the dunites (peridotite) and other basic magnesian rocks of Salem. When freshly broken it is of a dazzling white colour and hence the magnesite-veins traversing the country have been named the Chalk hills of Salem. The magnesite of Salem is of a high degree of purity, is easily obtained and, when calcined at a high tem­ perature, yields a material of great refractoriness. Other places in South India also contain magnesite-veins traversing basic rocks, viz Coorg, Coimbatore, Mysore and Trichinopoly. The industrial uses of magnesite are in the manufacture of refractory materials for use in the steel industries and as a source of carbonic acid gas. I t is also manu­ factured into cement (Sorel cement) for artificial stone, tiles, etc. The combined output of Salem and Mysore magnesite workings reach a total of about 15,000 tons, valued at Rs. one lac. Asbestos2 Two quite different minerals are included under this name : one a variety of amphibole resembling tremolite and the other a fibrous variety of serpentine (chrysotile). Both possess much the same physical properties th at make them valuable as commercial products. Asbestos (both the real mineral and chrysotile) has been discovered at many places in India, but at only a few localities to be of any com­ mercial use, viz. Pulivendla (Cuddapah), where excellent chrysotile asbestos occurs at the contact of a bed of Cuddapah limestone with a dolerite sill; in the Hassan district of the Mysore State and the Saraikala State of Singhbhum. Much of the latter, which is of the actinolite variety, however, does not possess th at softness or flexibility of fibre on which its industrial application depends. Asbestos has found a most wonderful variety of uses in the industrial world of to­ day, viz. in the manufacture of fire-proof cloth, rope, paper, mill­ boards, sheeting, belt, paint, etc., and in the making of fire-proof safes, insulators, lubricants, felts, etc. Asbestos (amphibole) occurs in pockets or small masses or veins in 1 Middlemiss, Rec. O.S.I. vol. xxix. pt. 2, 1896. 2 Coggin Brown, Bulletin of I. I. and L. No. 20, 1922; A. L. Coulson, Asbestos in Madras, Mem. O.S.I. vol. lxiv. pt. 2, 1934.

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the gneissic and schistose rocks. The chrysotile variety forms veins in serpentine. The available supplies in India are sufficient to meet any expansion of indigenous asbestos industry. In 1929 about 300 tons were produced from Madras and Sarai Kcla, but the extraction has fallen off now due to lack of demand.

calcium phosphate. Massive apatite occurs as an abundant consti­ tuent of the mica-pegmatites of Hazaribagh and of the mica-peridotite dykes in the Bihar coalfields and in some schistose rocks of Bom­ bay and Madras. I t is also found on a large scale in lenticular aggre­ gates in the Dharwar rocks of Dalbhum, in Singhbhum, where the phosphate is estimated to be present in 250,000 tons quantity. A source of phosphatic material for use as mineral fertiliser exists in the basic slag formed in the manufacture of steel. Over 30,000 tons of this slag is being dumped annually at the steel works for want of any present demand. India imports phosphatic manures of the value of Rs. 12 lacs annually. Mineral Paints

Barytes Barytes occurs at many places in India in the form of veins and as beds in shales, in sufficient quantities, but with few exceptions the deposits were not worked till late because of the absence of any demand for the mineral. The chief localities for barytes are Cuddapah and Kurnool1 districts ; Alwar S ta te ; Salem ; and Sleemanabad (in the Jabalpur district). Barytes is used as a pigment for mixing with white lead, as a flux in the smelting of iron and manganese, in paper-manufacture, in pottery-glazes, etc. The annual production approximates 5500 tons, valued at Rs. 41,500. Fluor-spar This mineral is of rather rare occurrence in India. Veins of fluorite occur in the rocks of some parts of the Peninsula and the Himalayas, in gneiss in Kishengarh, in the Vindhyan limestone in Rewah, in granite in the Sutlej valley, Simla Himalaya, but the quantity avail­ able is not considerable in any place. The chief use of fluor-spar is as a flux in the manufacture of iron, of opalescent glass, enamel, etc. Phosphatic Deposits2 Native phosphates, as apatite, or rock-phosphates, as concretions, are highly valued now as artificial fertilisers or manures, either in the raw condition or after treatment with sulphuric acid, to convert them into acid or superphosphates. Their rarity in a country like India, whose primary industry is agriculture, is most regrettable. The only occurrence of phosphatic deposits on a sufficient scale is in con­ nection with the Cretaceous beds of Trichinopoly, where phosphate of lime occurs in the form of septarian nodules disseminated in the claybeds. The quantity available is about 8,000,000 tons. A like deposit near Mussoorie, overlying the Deoban limestone, is very rich in tri1 A. L. Coulson, Mem. G.S.I. vol. lxiv. pt. 1, 1933. 2Sir Edwin Pascoe, India’s Resources in Mineral Fertilisers, Bull. I . / , and L. No. 42. 1929.

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Substances used for mineral paints—A number of rock and mineral substances are employed in the manufacture of paints and colouring materials in Europe and America. Substances w^hich are suitable for this purpose include earthy forms of haematite and limonite (ochres, geru) ; refuse of slate and shale quarries, possessing the proper colour and degree of fineness ; graphite ; laterite ; orpim ent; barytes ; asbestos ; steatite, etc. Many of the above substances are easily available in various parts of India and some are actually utilised for paints and pigments, viz. a black slate for making black paints ; laterite and geru (red or yellow levigated ochre) for red, yellow or brown colouring matters ; barytes as a substitute for white lead ; orpiment for yellow and red colours in lacquer work.1 Large quan­ tities of red and yellow ochre in association with graphite-bearing slate (carbon-content 25-30 per cent.) occur in the Salkhala system of deposits in the Uri Tehsil of Kashmir State. These minerals have been found suitable for manufacture of mineral paints.2 Uranium Pitchblende of Gaya—Pitchblende (Uraninite) occurs in nodular aggregates, in patches of basic segregations in a pegmatite vein cross­ ing the gneisses and schists in the Singar mica-mines at Gaya.3 I t is associated with other uranium minerals—uranium-ochre, torbernite, and also columbite, zircon, triplite, etc. These minerals have great 1 Coggin Brown, Bulletin of I. I. and L. No. 20, 1922. 2 C. S. Middlemiss, Mineral Surv. Rep. J. and K. State (Graphite and Ochre), Jammu,

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commercial value because of the small proportion of radium th at they contain. Recent investigations in the Gaya pitchblende deposits have proved that the latter are very promising in their radium-content. Further prospecting in the area, however, has not disclosed the pres­ ence of any considerable deposits of pitchblende. Besides pitchblende, other radium-bearing minerals and radio-active earths have been found. Samarskite, a complex niobate and tantalate, is found in the mica-bearing pegmatite of Nellore in masses weighing 200 lbs.

The most common of these are : wolfram and monazite, which have been already dealt with ; columbite and tantalite (niobates and tantalates of the rare-earths), which occur in the mica-pegmatites of Gaya, Hazaribagh, Nellore, e tc .; gadolinite (a silicate of the yttrium earths), which is found in a tourmaline-pegmatite associated with cassiterite in Palanpur; and molybdenite, which is found in the crystalline rocks of Chhota Nagpur, Godavari Agency, Madura and in the elaeolite-syenite-pegmatite of Rajputana and of Travancore. Another rare mineral, thorianite, has been found in Travancore and Ceylon, containing from 60-80 per cent, of thoria and a considerable amount of helium. Allanite occurs in the pegmatites of Nellore, with sipylite, a niobate of erbium with other rare earths. Zircon is found with uranium minerals and with triplite in the micamines of Gaya and in the nepheline-syenites of Coimbatore. Cyrtolite is a radio-active variety found in some of these localities. Platinum and iridium occur as rare constituents of the auriferous gravels of some parts of Burma.

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Titanium Titanium occurs in its two compounds, ilmenite and rutile, the former of which is of fairly wide distribution in the charnockites and other gneisses of the Peninsula and Rajputana. It occurs plentifully on the Travancore coast as black sand along with monazite sand. Here the concentration of the mineral, derived from the disintegration of its parent rock, has reached large volumes, covering a coast-line of 100 miles length from Nindikarai to Liparum, round Cape Comorin. In 1933 nearly 53,000 tons were exported ; value £62,000. The chief use of ilmenite is in the manufacture of white paints, the opacity and covering power of titanium-oxide being high. I t is also used in alloys with iron. Rutile is also abundantly distributed in small crystals throughout the crystalline schists of the Peninsula. Vanadium Vanadium-bearing iron-ore, containing V20 3 in quantity varying from 1-6 per cent., has recently been discovered in deposits of con­ siderable size, but with a fitful distribution of the Vanadium-content, in Mayurbhanj State. Its exact paragenesis and relation with the country-rocks are not yet known, but the ore occurs in association with basic intrusions in Dharwar schists. The Rare Minerals The rare minerals of India—The pegmatite veins of the crystalline rocks of India contain a few of what are called the rare minerals as their accessory constituents. The rare elements contained in them have found an extended use in modern industries such as mantlemanufacture, the manufacture of special kinds of steels, and other products of highly specialised uses in the present-day industries.1 1 Cahen and Wootton, Mineralogy of the Rarer Metals, 1912 (C. Griffin).

Pyrite and Sulphur Pyrite is a mineral of very wide distribution in many formations, from the oldest crystalline rocks to the youngest sediments, but nowhere is it sufficiently abundant to be of commercial utility in the preparation of sulphur and sulphuric acid. The economic value of pyrite1 lies in its being a source of sulphur and not as an ore of iron, because the high proportion of sulphur in it is injurious to the iron. The only occurrences of any considerable scale, are those of the pyritous shales of Kalabagh and the Dandot collieries on the SaltRange, but the chances of sulphur manufactured out of these deposits to compete against imported sulphur are very few, and no attem pt is made for its development. Large stores of sulphur exist in connection with metallic sulphides, notably of copper and lead, which, when they are worked in India for the recovery of the metals will liberate the sulphur, as well, in large amounts. Sulphur in small quantities is obtainable as a sublimation product from the crater of Barren Island volcano, and from some of the ex­ tinct volcanoes of Western Baluchistan, and was formerly worked at Sanni2 in the Kalat State. Many of the sulphur springs precipitate some quantities of fine powdery sulphur near their outlets. Sulphur 1 Fox, Bulletin of I . I . and L. No. 28, 1922. 2 Rec. G.S.I. toL xlvi. pt. 2, 1919.

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occurs in the Puga valley of Ladakh. I t is found there both as a deposit from its hot springs and also as filling up fissures in quartzschists. These sources are, however, too insignificant to meet the demand for sulphur in the country which is satisfied largely by imports from foreign countries. Large reserves of sulphur are available in the leadzinc-silver ores of Bawdwin (page 351). Sulphuric acid—Sulphur has many important uses, much the most important being the manufacture of sulphuric acid. With regard to the last-named compound we may quote the following valuable state­ ment : “ Sulphuric acid is a key to most chemical and many metal­ lurgical industries ; it is essential for the manufacture of superphos­ phates, the purification of mineral oils, and the production of ammon­ ium sulphate, various acids, and a host of minor products ; it is a necessary link in the chain of operations involved in the manufacture of alkalies, with which are bound up the industries of making soap, glass, paper, oils, dyes, and colouring matter ; and, as a bye-product, it permits the remunerative smelting of ores which it would be impos­ sible otherwise to develop. During the last hundred years the cost of a ton of sulphuric acid in England has been reduced from over £30 to under £2, and it is in consequence of the attendant revolution in Europe of chemical industries, aided by increased facilities for trans­ port, that in India the manufactures of alum, copperas, blue vitriol and alkalies have been all but exterminated ; th at the export trade in nitre has been reduced instead of developed ; that the copper and several other metals are no longer smelted ; th at the country is robbed every year of over 90,000 tons of phosphate fertilisers, and that it is compelled to pay over 20 millions sterling for products obtained in Europe from minerals identical with those lying idle in India.” 1

^ SOILS Soil formation—The soils of all countries are, humanly speaking, the most valuable part of the regolith or surface rocks and constitute in many cases their greatest natural asset. They are, broadly speaking, either the altered residue of the underlying rocks, after the other sol­ uble constituents are removed, mingled with some proportion of de­ composed organic m atter (residual soilY^ or the soil-cap may be due to the deposition of alluvial debris brought down by the rivers from 1Rec. G.S.I. vol. xlvi. 1915, p. 295.

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the higher grounds (drift soil). The origin and growth of soils, how­ ever, is a subject of great complexity involving a long series of changes ending in the production of the clay-factor and other colloids of the soils. The soil of the Peninsula, for the greater part, is of the first de­ scription, while the great alluvial mantle of North India, constituting the largest part of the most fertile soil of India, is of the second class. We can easily imagine th at in the production of soils of the first kind, besides the usual meteoric agencies, the peculiar monsoonic conditions of India, giving rise to alternating humidity and desiccation, must have had a large share. These residual soils of the Peninsula show a great variety both in their texture and in their mineralogical composi­ tion, according to the nature of the subjacent rock whose waste has given origin to it. They also exhibit a great deal of variation in depth, consistency, colour, etc. However, the soils of India, so far as their geological peculiarities are concerned, show far less regional variation than those in other countries, because of the want of variety in the geological formations of India.1 Broadly speaking the soils of the Indian Peninsula differ markedly from the soils of European countries, which are largely of post-Glacial growth and in which the pedogenic processes have not been in opera­ tion long enough to mature them. The latter soils have close affinities with their rocky substratum, both as regards composition and morph­ ology. Podsolisation is a common character of these soils. In both these respects the soils of Peninsular India offer a contrast and, being far older than the Glacial period of Pleistocene age, have attained full maturity. The effect of these factors is to introduce many changes in the composition, structure and texture and to modify profoundly the clay-factor of the soils. This is best seen in the two characteristic Indian soils—laterite and black-cotton soil. Podsols, except among some mountain and forest soils of North India, are uncommon in the rest of the country. The alluvial soils of the vast Indo-Gangetic plains likewise differ from Peninsular soils’and from the majority of European soils in having undergone but little pedogenic evolution since their deposition by river agency, so late as in sub-Recent times. They are still largely immature and have not developed any character­ istic soil profile, or differentiation into zones. The soils of South India—Over the large areas of metamorphic rocks the disintegration of the gneisses and schists has yielded a shallow sandy or stony soil, whereas th at due to the decomposition of the basalts of 1 The Geological Foundations of the Soils of India, Rec. G.S.I., vol. lxviii, pt. 4, 1935.

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the Deccan, in the low-lying parts of the country, is a highly argil­ laceous, dark, loamy soil. This soil contains, besides the ordinary in­ gredients of arable soils, small quantities of the carbonates of calcium and magnesium, potash, together with traces of phosphates, ingred­ ients which constitute the chief material of plant-food that is absorbed by their roots. The latter soil is, therefore, much more fertile as a rule than the former. The soil of the metamorphic rocks is thin and shallow in general (except where it has accumulated in the valleybasins), because of the slowness with which the gneisses and schists weather. The soil in the valleys is good, because the rain brings the decomposed rock-particles and gathers them in the hollows. In these situations of the crystalline tract the soils are rich clay-loams of great productiveness. Soils of sedimentary rocks—The soils yielded by the weathering of the sedimentary rocks depend upon the composition of the latter, whether they be argillaceous, arenaceous or calcareous, and upon their impurities. Soils capping the Gondwana outcrops are in general poor and infertile, because Gondwana rocks are coarse sandstones and grits with but little of cementing material. They are thin sandy soils, capable of supporting tillage only with copious manuring. Argil­ laceous and impure calcareous rocks yield good arable soils. Refer­ ence must here be made to the remarkable black soil, or regur of large areas of the Deccan which has already been described on page 304. The greater parts of Rajputana, Baluchistan and the Frontier Provinces are devoid of soils, because the conditions requisite for the growth of soils are altogether absent there. The place of soil is taken by another form of regolith, e.g. wide-spread scree and talus-slopes, coluvial gravels, blown sand and loess. In the Himalayan region soilformation is a comparatively rapid process, the damp evergreen forests playing an important part in the generation and conservation of the soil-cap. The unforested southern slopes of these mountains are generally devoid of s6il covers. Likewise deforestation of some tracts of the outer Himalayas has been followed by a stripping of their soil-cover, due to accelerated erosion of the unprotected surface.1

The loess caps of the higher parts of the Punjab possess many of the qualities of an excellent soil, but its high porosity tends to lower the underground water-table to inaccessible depth. Alluvial soils—The alluvial soils of the great plains of the Indus and Ganges, as also of those of the broad basins of the Peninsular rivers, are of the greatest value agriculturally. They show minor variations in density, colour, texture and porosity, moisture-content and in the composition of their clay-factor. In spite of minor difference in com­ position, from district to district, in general they are light-coloured loamy soils of a high degree of productiveness, except where it is de­ stroyed by the injurious reh salts. There are, however, a number of physical and organic factors which determine the characters and peculiarities of soils and their fertility or otherwise ; this subject is, however, beyond the scope of this book and cannot be discussed further.1 (See pages 305 and 366.)

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1 In the past few years attention is being forcibly drawn to the increasing aridity of parts of the Hoshiarpur district of the Punjab, the northward progress of the sands from the southern desert, the deepening of the water-table and the gullying and erosion of tracts that were, three or four generations ago, covered under a fertile soil-cap. These adverse effects are ascribed to the destruction of forests which once clothed the Siwalik foot-hills. Similar effects have been noticed in other sub-montane districts also and serve to impress the important role played by forests in moderating the denudation by rain, in regulating the run off, in conserving the sub-soil water and in binding and pro­ tecting the soil-cap from wind and water erosion.

1 The following books on study of soils may be consulted : G. W. Robinson, Soils— Their Origin, Constitution and Classification, London, 1932 ; P. Vegeler, Tropical Soils, London, 1933.

GEOLOGY OF K A SH M IR

CHAPTER X X V II.

(A PPEN D IX )

GEOLOGY OF KASHMIR T h e object of the present chapter is to give in brief outline the geology of a province which contains, within a small geographical compass, one of the finest developments of the stratified record seen in the Indian region and perhaps in the world. In describing the geology of Kashmir passing references will be made to the adjoining districts of Hazara and Simla. These three provinces are connected by some common features and have received more attention from geologists than other areas of the Himalayas. A very large section of the fossiliferous geo­ logical record is exhibited in the hills and mountains surrounding the beautiful valley of Kashmir in localities easily accessible to students, and thus offering facilities for the study of the stratigraphical branch of the science, which are met with in no other parts of India. In this happy combination of circumstances the Vale of Kashmir is unique as an excursion ground for students of geology, as much for its wealth of stratigraphic results, as for its physiographic phenomena, its oro­ graphic features, its glaciers, etc. We shall describe in the present chapter the geology and physical features of the country comprising the territories of the Jammu and Kashmir State, with some sketch notes on the geologically surveyed parts of Hazara on the west and Simla-Chakrata on the east, con­ stituting a large area in the North-West Himalaya. Incidentally, therefore, the subject of this chapter will also be a recapitulation of the main facts of the orography and geology of the best explored parts of the Himalayas. Even within this there are large districts which are geologically unknown, e.g. the portion east of the Ravi and west of the Sutlej is yet largely unexplored ground, while districts such as Baltistan, Zanskar and Ladakh are very imperfectly known.

PHYSICAL FEATURES The orographic features—There is a close uniformity in physical features and geological constitution of the sub-Himalayan tract from Rawalpindi to Dehra Dun, covered by the Siwalik and Sirmur rock3S2

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systems. A description of the Jammu hills may be taken broadly as a type. An admirable account of the geography of the Kashmir-Himalayan region is given by Frederick Drew in his well-known book. Jammu and Kashmir Territories (E. Stanford, London, 1875). What follows in this section is an abridgement from this author’s description, modified, to some extent, by incorporating the investigations of later observers. The central Himalayan axis, after its bifurcation near Kulu, runs as one branch to the north-west, known as the Zanskar Range, terminat­ ing in the high twin-pfeaks of Nun Kun (23,447) (“ the Great Himalaya Range ” of Burrard) ; the other branch runs due west, a little to the south of it, as the Dhauladhar Range, extending further to the north­ west as the high picturesque range of the Pir Panjal, so conspicuous from all parts of the Punjab. Between these two branches of the crystalline axis of the Himalayas lies a longitudinal valley with a south-east to north-west trend, some 84 miles long and 25 miles broad in its middle, the broadest part. The long diameter of the oval is parallel to the general strike of the ranges in this part of the Hima­ layas. The total area of the Kashmir valley is 1900 sq. miles, its mean level about 5200 feet above the sea. The ranges of mountains which surround it at every part, except the narrow gorge of the Jhelum at Baramula, attain, to the north-east and north-west, a high general altitude, some peaks rising above 18,000 feet. On the south-western border, the bordering ridge, the Pir Panjal, is of comparatively lower altitude, its mean elevation being 14,000 feet. The best known passes of the Pir Panjal range, the great high-ways of the past, are the Panjal Pass, 11,400 fe e t; the Budil, 14,000 fe e t; Golabghar Pass, 12,500 fe e t; the Banihal Pass, 9300 fe e t; Tata K uti and Brahma Sakai are the highest peaks, above 15,500 feet in elevation. The Outer Ranges (the Sub-Himalaya or the Siwalik Ranges) The simple geological structure of the outer ranges. The “ duns ” —The outermost ranges of the Kashmir Himalaya rise from the plains of the Punjab, commencing with a gentle slope from Jammu, attain to about 2000 feet altitude, and then end abruptly in steep, almost perpendicular, escarpments inwards. Then follows a succession of narrow parallel ridges with their strike persistent in a N. W.-S.E. direc­ tion, separated by more or less broad longitudinal or strike-valleys (the basins of subsequent streams). These wide longitudinal or strikevalleys inside the hills are of more frequent occurrence in the eastern parts of the Himalayas, and attain a greater prominence there, being

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V known there as ‘ duns ” (e.g. Dehra Dun, Kothri Dun, Patli Dun, etc.). In the Jammu hills the extensive, picturesque duns of Udhampur and Kotli are quite typical. The Kashmir valley itself may be taken as an exaggerated instance of a dun in the middle Himalaya. These outer hills, formed entirely of the younger Tertiary rocks, rarely attain to greater altitude than 4000 feet or thereabouts. The outer ranges of the sub-Himalayan zone, bounded by the Ravi and the Jhelum, the two east and west boundaries of the Kashmir State, are known as the Jammu hills. Structurally, as well as lithologically, they partake of the same characters as are seen in the hills to the east and west of it, which have received a greater share of attention by the Indian geo­ logists. Ranges situated more inwards, and formed of older Tertiary rocks (of the Murree series), reach a higher altitude, about 6000 to 8000 feet. At the exit of the great rivers, the Chenab and the Jhelum, there is an indentation or a deep flexure inwards into this region corres­ ponding to an abrupt change in the direction of the strike of the hills. In the case of the Jhelum a t Muzafferabad this flexure is far more conspicuous and significant, the result of the syntaxial bend of the whole mountain-system, the strike of the whole Himalayan range there changing from the usual south-east—north-west to north and south and thence undergoing another deflection to north-east— south-west. (See p. 314.) The Middle Ranges (Lesser or Middle Himalayas—The Panjal and Dhauladhar Range)1 The Panjal Range. “ Orthoclinal ” structure of the Middle ranges— This region consists of higher mountains (12,000-15,000 feet) cut into by deep ravines and precipitous defiles. The form of these ranges bears a great contrast to the outer hills described above, in being ridges of irregular direction th at branch again and again, and exhibit­ ing much less correspondence between the lineation of the hills and the strike of the beds constituting them. In the Pir Panjal, a singu­ larly well-defined range of mountains extending from the Kaghan valley to beyond the Ravi valley, which may be taken as a type of the mountains of the Middle Himalaya, these ridges present generally a steep escarpment towards the plains and a long gentle slope towards Kashmir. Such mountains are spoken of as 1. /ing an “ orthoclinal ” 1 For a connected account of the geology of Pir Panjal, see Middlemiss, Rec. vol. xii. pt. 2, 1911, and Wadia, Geology of Poonch and Adjoining Area, Mem. O.S.I., vol. Ii. pt. 2, 1928.

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structure, with a “ writing-desk ” shape (see Fig. 38, p. 391). To this cause (among several others) is due the presence of dense forest vege­ tation, the glory of the Middle Himalaya, clothing the north and north-eastern slopes, succeeded higher up by a capping of snows, while the opposite, southern slopes are, except in protected valley-slopes, barren and devoid of snow, being too steep to maintain a soil-cap for the growth of forests or allow the winter-snows to accumulate. South-east of the Ravi, the Pir Panjal is continued by the Dhauladhar range, passing through Dalhousie, Dharamsala and Simla. Geo­ logically the middle Himalaya of this part are different from the foot­ hills, being composed of a zone of highly compressed and altered rocks of various ages, from the Purana and Carboniferous to Eocene. The axial zone of the Panjal range is composed of the Permo-Carboni­ ferous. For map of the Pir Panjal, see PI. XV. Inner Himalayas The zone of highest elevation. Physical aspects of the inner Hima­ layas—To the north of the Pir Panjal range, and enclosing between them the valley of Kashmir, are the more lofty mountain-ranges of the innermost zone of the Himalayas, rising above the snow-line into peaks of perpetual snow. In the North Kashmir range an offshoot of the Zanskar range, which forms the north-eastern border of the valley, there are peaks of from 15,000 to 20,000 feet in height. Beyond this range the country, with the exception of the deep gorges of the Middle Indus, is a high-level plateau-desert, utterly devoid of all kind of vegetation. Here there are elevated plateaus and high mountainranges separated from one another by great depressions, with majestic peaks towering to 24,000 feet. The altitude steadily increases farther north, till the peak K 2, on the mighty Karakoram or Mustagh range, attains the culminating height of 28,265 feet—the second highest mountain in the world. The Karakoram chain is the watershed be­ tween India and Turkestan. The valleys of these regions show vary­ ing characters. In the south-east is the Changchenmo whose width is from five to six miles, with a mean height of 14,000 feet above the sealevel. From th at to the north-west the height of the valley-beds de­ scends, till in Gilgit on the very flanks of the gigantic peak of Nanga Parbat, Diyamir, (26,620 feet), the rivers have cut so deeply through the bare, bleak mountains that the streams flow at an elevation of only 5000 and, in one case, 3500 feet above the level of the sea. At places, in north and north-east Kashmir, there are extensive flat, wide, plains w . g .i .

2b

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or depressed tracts among the mountains, too wide to be called val­ leys, of which the most conspicuous are the plateaus of Deosai, 13,000 feet high, Lingzhitang, 16,000 feet, and Dipsang of about the same height. The physical features of this extremely rugged, wind-swept and frost-bitten region vary much in character. They present an aspect of desolate, ice-bound altitudes and long dreary wastes of valleys and depressed lands totally different from the soft harmony of the Kash­ mir mountains, green with the abundance of forest and cultivation. The rainfall steadily diminishes from the fairly abundant precipita­ tion in the outer and middle ranges to an almost total absence of any rainfall in the districts of Ladakh and Gilgit, which in their bleakness and barrenness partake of the character of Tibet. Ladakh is one of the loftiest inhabited regions of the world, 12,000-15,000 feet. Its short but warm summers enable a few grain and fruit crops to ripen. Owing to the great aridity of the atmosphere, the climate is one of fierce extremes, from the burning heat of some of the desert tracts of the Punjab plains in the day, to several degrees below freezing-point at night. Baltistan, lying directly to the north of Kashmir, and receiv­ ing some share of the atmospheric moisture, has a climate intermediate between the latter and that of Ladakh. In consequence of the great insolation and the absence of any water-action, there has accumulated an abundance of detrital products on the dry uplands and valleys forming a peculiar kind of mantle-rock or regolith of fresh, undecomposed rock-fragments. The bare mountains which rise from them exhibit the exquisite desert coloration of the rocks due to the peculiar solar weathering. Between Ladakh and the Dhauladhar range are the districts of Zanskar, Lahoul and Rupshu, consisting of intricately ramifying glaciated ranges of crystalline rocks, intersected by lofty valleys having but a restricted drainage into a few saline lakes and marshes. This rugged country is crossed by a few trade-routes from Simla and Kulu to Tibet, through high passes, 16,000 to 18,000 feet. With the exception of a part of Ladakh, which consists of Tertiary rocks and a basin of Mesozoic sedimentary rocks on the northern flank of the Zanskar mountains, by far the larger part of the inner moun­ tains is composed of igneous and metamorphic rocks—granites* gneisses and schists. There is no counterpart of the Kashmir basin north of the Dhaul­ adhar in the Simla mountains. East of the Sutlej the Dhauladhar range approaches and closes in with the Great Himalaya Range. The important Spiti basin of Palaeo-Mesozoic sediments lies to the north of the crystalline gneissic axis of the latter.

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Valleys The transverse valleys. The configuration of the valleys—In con­ formity with the peculiarities of the other Himalayan rivers, briefly referred to in the chapter on physical features, the great rivers of this area—the Indus, Jhelum, Chenab, Ravi and Sutlej—after running for variable distances along the strike of the mountains, suddenly make an acute bend to the south and flow directly across the mountains. The Sutlej, like the Indus, takes its origin in Tibet, much to the north of the Indo-Tibet watershed. Just a t the point of the bend, a large tributary joins the main stream and forms, as it were, its upward con­ tinuation. The Gilgit thus joins the Indus at its great bend to the south ; the Ward wan joins the Chenab at its first curve in Kishtwar, and the Ans at its second curve plain wards, above Riasi. The Kishenganga and the Kunhar meet the Jhelum at Domel, where the latter takes its acutest curve southwards before emerging into the Punjab. Similarly the Spiti river joins the Sutlej where the latter takes its final southward turn. These transverse, inconsequent valleys of the Hima­ layas, as we have seen before, are of great importance in proving the antiquity of the Himalayan rivers, an antiquity which dates before the elevation of the mountain-system (see page 20). The configuration of the valleys in the inner Himalaya of the Kashmir regions is very peculiar, most of the valleys showing an abrupt alternation of deep U-shaped or I-shaped gorges, with broad shelving valleys of an open V-shape. This is due to the scanty rainfall, which is powerless in eroding the slopes of the valley where they are formed of hard crystal­ line rocks and where the downward corrasion of the large volume of streams produced by the melted snows is the sole agent of valleyformation. The broad valleys which are always found above the gorge-like portions are carved out of soft detrital rocks which, having no cover of vegetation or forest growth to protect them, yield too rapidly to mechanical disintegration. Many of the valleys are very deep. This is particularly seen in Drava, Karnah and Gilgit. By far the deepest of all is the Indus valley in Gilgit, which a t places is bor­ dered by stupendous precipices 17,000 feet in height above the level of the water at its bed. That this enormous chasm has been excavated by the river by the ordinary process of river-erosion would be hard to believe were not the fact conclusively proved by the presence of small terraces of river gravels at numerous levels above the present surface of its waters. At Shipki the Sutlej receives its principal tributary, the Spiti river,

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which has drained the wide synclinal basin of marine Palaeozoic and Mesozoic sediments. Up to this point the Sutlej is a strike-valley, flowing along the whole length of the alluvial plateau of Hundes in a profound 3000 feet canon, excavated through horizontally bedded ossiferous Pleistocene boulder gravel and clay, deposited by itself at a former stage of its history. Below Shipki the river turns south and traverses a variety of geological formations of the Zanskar and the Great Himalaya range, in narrow gorges th at are 10,000 feet deep at places, with perpendicular rock-cliffs of 6000 to 7000 feet sheer fall. Its passage through the sub-Himalayan Tertiary zone below Simla shows that the river at various stages must have been impeded and deflected in its course again and again by its own deposits. From the presence of numerous terraces of lacustrine silt along the channel, the former presence of a chain of lakes all along the course of the Sutlej through the high mountains is indicated. This feature it shares with the Jhelum, Chenab and the Kunhar. Lakes There are very few lakes in Kashmir, contrary to what one would expect in a region of its description. The few noteworthy lakes are, the Wular in the valley, the salt-lakes of Ladakh, bearing evidence of a progressive desiccation of the country, viz, the Tsomoriri in Rupshu, which is 15 miles long and 2 to 5 miles wide and about 15,000 feet high ; the Pangkong in Ladakh, which is 40 miles long, 2 to 4 miles wide and 14,000 feet in elevation. The origin of the tw^o last-named lakes is ascribed by Drew to the damming of old river courses by the growth of alluvial fans or dry-deltas of their tributary streams across them. These lakes have got several high-level beaches of shingle and gravel resting on wave-cut terraces marking their successive former levels at considerable heights above the present level of the water. The wide, level valley-plains of the Changchenmo, Dipsang and Lingzhitang, at an elevation of from 16,000-17,000 feet, may be re­ garded as of lacustrine origin, produced by the desiccation and silting up of saline lake-basins without any outlet. There are a number of smaller lakes or tarns, both in the valley of Kashmir proper and in the bordering mountains, most of which are of recent glacial origin, a few of which may be true rock-basins. The source of the Sutlej is now known to be the two sacred ice­ bound lakes of Manasarowar and Rakas Tal, situated behind the Himalayan water-shed at an altitude of 16,000 feet to the south of the

GEOLOGY OF K A SH M IR

389

peak of Kailas. Sven Hedin has proved that the Sutlej flows from the Rakas Tal, which derives its water by subterranean drainage from the adjacent Manasarowar and not usually through any visible channel. Glaciers Transverse and longitudinal glaciers—In Drew’s work, already men­ tioned, there is a snow-map of Kashmir which admirably shows the present distribution of glaciers and snow-fields in the Kashmir and the adjacent regions. With the exception of a few small glaciers in the Chamba mountains, there are no glaciers in the middle and outer Himalayas at present. In the Zanskar range glaciers are numerous though small in size ; only at one centre, on the north-west slopes of the towering Nanga Parbat (26,620 feet), they appear in great num­ bers and of large dimensions. One of these (the Dayamir) descends to a level of 9400 feet above the sea, near the village of Tarshing. North and north-east of these no glaciers of any magnitude occur till the Hunza valley on the south of the Mustagh, or Karakoram, range is reached, whose enormous snow-fields are drained by a number of large glaciers which are among the largest glaciers of the world.1 The southern side of this stupendous mountain-chain nourishes a number of gigantic glaciers some of which, the Biafo, the Baltoro, the Siachen, the Remo, and the Braldu glaciers, are only exceeded in size by the great Humboldt of Greenland. There are two classes of these glaciers : those which descend transversely to the strike of the mountains and those which descend in longitudinal valleys parallel to the trend of the mountains. The latter are of large dimensions and are more stable in their movements, but terminate at higher elevations (about 10,000 feet) than the former, which, in consequence of their steeper grade, descend to as much as 8000 to 7000 feet. The Biafo glacier of the Shigar valley reaches nearly 40 miles in length and the Hispar 25 miles. The lowest level to which glaciers descend in the Kashmir Himalayas is 8000 or even 7000 feet, reaching down to cultivated grounds and fields fully 4000 feet lower than the lower-most limit of the glaciers in the eastern Himalayas of Nepal and Sikkim. Many of these glaciers show secular variations indicative of increase or diminu­ tion of their volumes, but no definite statement of general application can be made about these changes (p. 15). The majority of them, like the Tapsa, are receding backwards, leaving their terminal moraines in 1 For results of exploration of Karakoram and Baltistan glaciers, papers by Dainelli and Mason may be consulted.

F ig . 37.—View of the great Baltoro Glacier. (From a drawing by Col. Godwin Austen.)

glaciers, although there are no indubitable proofs of their ever having descended to the plains of the Punjab, or even to the lower hills of the outer Himalayas. Large transported blocks are frequently met with at various localities, a t situations, in one case, but little above 4000 feet. The Jhelum valley between Uri and Baramula contains a num­ ber of large boulders of granitoid gneiss brought from the summit of the Kaj Nag range (to the N.W.), some of which are as large as cot­ tages. These are common phenomena in all the other valleys ; rockpolishing and grooving are well seen on the cliff-faces of the Lidar, Sind, and their tributaries, while typical roches moutonnees are not rare on the hard, resistant rock-surfaces in the beds or sides of these valleys. In the Sind valley, near the village of Hari (6500 feet) on the road to Sona Marg, Drew has seen a well-grooved roche moutonnee. A little higher up, at Sona Marg itself (9000 feet), are seen undulating valleys made up entirely of moraines. In the valley of Kashmir proper some of the fine impalpable buff-coloured sands and laminated clays, inter­ stratified among the Karewa deposits, are of glacial origin (“ rock meal ”), formed during melting of the ice in inter-glacial periods. 1 For glaciers of the Hunza valley, see Rec. Q.8.I. vol. xxxv. pts. 3 and 4, 1907.

The whole north-east side of the Panjal range and to a less extent elevations above 6500 feet on the south-west are covered thickly under an extensive ac­ cumulation of old moraine materials, which have buried all its solid geology (see Fig. 38). In northern Baltistan, where the existing glaciers attain their maximum development, there are other characteristic proofs of old glaciation at far lower levels than the lowest limits of modern glaciers ; polished rock-surfaces, rock-groovings, perched blocks, etc., occur abundantly in the Braldu valley of this district. Many of the valleys of this region in their configuration are of a U-shape, which later denuding agencies are trying to change to the normal V-shape. Desiccation of lakes—The well-marked desiccation of the lakes of Skardu, Rupshu and the other districts of north and north-east Kashmir, is a very noteworthy phenomenon and has an important bearing on this question. The former higher levels of their waters point to a greater rainfall and humidity connected with the greater cold of a glacial period. The Tsomoriri has a terrace or beach-mark at a height of 40 feet above the present level of its waters. The Pangkong lake has similar beaches at various levels, the highest being 120 feet above the surface of the present lake. STRATIGRAPHY OF KASHMIR Introduction—The late Mr. R. Lydekker in the ’eighties of the last century, made a geological survey of Kashmir. His results

391

(Middlemiss, Geological Survey of India,

front of them, which have become covered by grass and in some cases even by tre e s; but others, like the Palma glacier, are steadily ad­ vancing over their own terminal moraines.1 Proof of Pleistocene Ice Age—There are abundant evidences, here as everywhere in the Himalayas, of the former greater development of

GEOLOGY OF K A SH M IR

Rec. xli. pt. 2.)

GEOLOGY OF IN D IA

F ig 3& —Section of the Pir Panjal across the N.E. slope from Nilnag—Tatakuti.

390

392

GEOLOGY OF IN D IA

were published in a Memoir of the Geological Survey of India (vol. xxii. 1883). Lydekker in his preliminary survey grouped all the stratified formations of Kashmir into three broad divisions—t]ie Panjal, the Zanskar and the Tertiary groups—the homotaxial relations of whose constituent series and systems were not clearly distinguished because of the absence of satisfactory fossil evidence. Mr. C. S. Middlemiss, F.R.S., worked in the same field from 19081917. Middlemiss’s researches have revealed a series of fossiliferous strata, in different parts of the province, belonging to various divisions of the Palaeozoic and the Mesozoic, which have enabled him to make a more perfect classification of the Kashmir record. Thus he has resolved what was formerly one comprehensive group, the Panjal system, which encompassed almost the whole of the Palaeozoic sequence, into no less than seven well-defined systems or series, the representatives of the Cambrian, Ordovician, Silurian, Devonian, Carboniferous and Permian, and the homotaxial equivalents of those of the classic ground of Spiti. Of the Mesozoic systems the Trias is the best and most fully de­ veloped ; the Jurassic and Cretaceous outcrops are few and mostly confined to the mountains of Ladakh which have scarcely been sys­ tematically surveyed by geologists. All the Tertiary systems are fully represented in the outer mountains and have been studied by a num­ ber of workers. As stated on page 314 the broad outlines of the stratigraphy of Hazara and North-West Kashmir are similar ; these two regions form one more or less continuous sedimentary terrain, though now isolated by the deep knee-bend of the mountains across the Muzaffarabad pro­ montory of the foreland. A great regional unconformity encompass­ ing the period from the top of the Silurian to the Middle Carboniferous is a distinctive feature of this north-west province. The south-east part of Kashmir has a continuous Palaeozoic record, similar to that of Spiti. The account given in the following pages is deduced from the writ­ ings of Lydekker, Middlemiss and Wadia. For more detailed infor­ mation with regard to the whole of the Palaeozoic group and the Triassic system, the student should consult original publications, Rec. G.S.I. vol. xl. part 3, 1910, and vol. lxviii. part 2, 1934. For the remaining systems, and the tectonics of Kashmir, the present writer’s work should be consulted.1

393

GEOLOGY OF K A SH M IR

[The geographical disposition of the m ain sedim entary belt in the K ash­ mir H im alayas calls for an explanation. W hile in the rest of the H im alayas the zone of marine sedim ents is w holly beyond, i.e. north of, the crystalline axis, in the Kashm ir portion the m ost im portant sedim entary basin lies be­ tw een tw o bifurcations of th at axis, and in this w ay effaces th at distinction betw een th e “ H im alayan ” and “ T ibetan ” zones so clearly marked in the other parts of the m ountains. The distinction betw een th e m iddle (H im alayan) and th e outer (subH im alayan) zones is, however, as clearly observable in this as in the other parts of the H im alayas. In th e province of H azara this confusion betw een the three H im alayan stratigraphic zones is still more marked.] 4

THE STRATIGRAPHY OF THE SIMLA HIMALAYA In the geosynclinal belt of the inner Himalayas of Spiti, Garhwal and Kumaon, at the back of the crystalline axis, a complete sequence of marine Palaeozoic and Mesozoic, in some respects more complete than in Kashmir, is developed. The stratigraphy of the Spiti sequence from Cambrian to Cretaceous, has been described by the late Sir Henry Hayden in Memoirs, vol. xxxvi, 1904. No further work has been done in this area since then. Of late years the stratigraphy and structure of the Simla mountains to the south of the crystalline axis is being worked out in detail by Pilgrim, West and Auden. A considerable amount of work has been accomplished in the crystalline metamorphics and the Purana com­ plex of this region and the structural disposition of the various belts of these rocks between Simla and Chakrata settled by the discovery of un­ conformities and thrust-planes. Geological work in this region has to contend against the serious difficulty of total absence of fossils in the vast formations of slate, limestone and sandstone, presumably of Palaeozoic and Mesozoic ages, which intervene between the Archaean and the scantily fossiliferous Eocene. While the cause of the absence of fossils from this large section of the geological column is yet an un­ solved problem, painstaking and accurate field work has made it pos­ sible to arrange and group the various formations of this area as near as possible in their natural order of superposition. With the doubtful exception of the Simla slates, which may be re­ garded as partly of Cambrian age, and an overlying group of inde­ terminate Lower Palaeozoic horizon, the Jaunsar series, allied lithologically to the equally obscure Tanawal (lower part) group of HazaraKashmir, the whole of the Lower and Middle Palaeozoic is missing from the Simla region. The next younger formation, the Blaini series,

w

Kashmir.

7000 ft.

Murree series.

Eocene—Nummulitics of Pir Panjal and Outer hills; Volcanics of Dras, Ladakh and ? Burzil.

^TLaki series. Nummulitics Ranikot 2000 ft. [ series.

Chikkim series— Orbitolina limestone and Volcanics of Burzil. Spiti shales. Megalodon (Kioto) limestone. Jui'assic of Banihal and ? Baltal. ("Upper, 5000 ft. Trias < Middle, 1200 ft. I Lower, 300 ft. Zewan series, 800 ft. Lower Gondwanas— Gangamopteris beds, 800 ft. [ Upper Tanawals of Pir Panjal (many thou­ sand ft.). Agglomeratic slates. ? Sirban limestone of Uri and Riasi > 1500 ft. Agglomeratic slates, 5000 ft.

Chikkim series, 10 ft. Giumal series, 300 ft. Spiti shales, 100 ft. Lower Jurassic (Oolite).

Age.

Pleistocene. Glacial moraines. Hundes alluvium. Siwaliks of the foot-hills.

Upper Trias, 1000 ft.

Panjal Trap > 5000 ft. Agglomeratic Slate. ^ Panjal Trap. § Sirban limestone § 2000 ft. ^ Speckled sandstones. Tanakki boulder-beds. ► §*

Pliocene. Miocene.

Kasauli series. Dagshai series. Nummulitics of Hundes. Subathu of the Outer Himalayas. Flysch series. Chikkim series. Giumal series. Spiti shales. Tagling limestone. Para limestone. Upper Trias. Muschelkalk. Lower Trias.

? Oligocene. Eocene. Cretaceous.

Jurassic. Triassic. Permian.

Productus shales Productus conglomerate. Blaini boulder-beds.

Upper Carboniferous.

;-------

Hazara.

Kashmir.

Po series.

Fenestella series > 2000 ft. Syringothyris limestone, 3000 ft.

*3 d fH P

Muth quartzite, 3000 ft. Silurian of Lidar and Sind. Ordovician of Hundawar and Lidar. Upper Cambrian of Hundawar, 5000 ft. Lower Cambrian of Shamsh Abari, 3000 ft.

Age.

Spiti-Simla.

Lipak series.

. ,3 | **

Lower Tanawal.

Hazara and Attock slate.

InfraKrol.

Muth quartzite. Silurian. Ordovician. Haimanta system. Simla slate.

^ 5 .| J 1g 5* oS%

Middle Carboniferous. Lower Carboniferous. Devonian. Silurian. Ordovician. Cambrian. ? Lower Cambrian.

Dogra slate, 5000 ft., passing into Lr. Cambrian

•E

1o

oI> f-t

|" Salkhala series (many thousand feet). Gneisses and granulites with intrusive granite and basic plutonics.

\

Salkhala series.

Jutogh and Chail series. Vaikrita series.

Algonkian.

Ortho- and para-gneisses and schists with acid and basic intrusives.

Gneisses and Schists with intrusives. ? Chor granite.

Archaeah.

396

G E O L O G Y O F IN D IA

is correctable, on convincing grounds, with an important datum-plane in Indian stratigraphy, the Lower Gondwana Ice age (Permo-Car­ boniferous), succeeded by a series of formations which find a more or less approximate parallel with the unfossiliferous Permian of Hazara. The Mesozoic group, except for the occurrence of the Jurassic Tal series, with its imperfect fauna suggesting affinities with the Spiti Jurassic,, is probably entirely missing. The Tertiary sequence is well exposed in the sub-Himalayan belt of the Simla region and its stratigraphy does not differ materially from th at of the North-West, the rocks, structure and classification being broadly alike in the two areas.1 The table on pp. 394, 395 gives an idea of the geological record as exposed in Kashmir, Hazara and Simla areas. ARCHAEAN AND PRE-CAMBRIAN The Crystalline Complex. “ Fundamental Gneiss ” with intrusive granites—Crystalline rocks, granites, gneisses and schists occupy large areas of the N.W. Himalayas of Kashmir and Simla, to the north of the Middle Ranges, forming the core of the Dhauladhar, the Zanskar and the ranges beyond in Ladakh and Baltistan. These rocks were all regarded as igneous and called “ Central Gneiss ” by Stoliczka and were taken to be Archaean in age. Later investigations have proved that much of this gneiss, as is the case with th at of the Himalayas as a whole, is not of Archaean age, but is of intrusive origin and has in­ vaded rocks of various ages at a number of different geological periods. Also a considerable part of this crystalline complex has now been found to be of pre-Cambrian metamorphic sedimentary origin, form-, ing the basement on which all the subsequent geological formations rest. The latter have been distinguished as the Salkhala series in the Kashmir-Hazara area and as Jutogh series in the Simla-Chakrata area. Some affinity of these series with the Dharwars of Rajputana and Singhbhum is apparent; while it is difficult or impossible to de­ marcate the areas of truly Archaean gneiss from the wide-spread later intrusive granites, the distinction of the sedimentary Archaeans from the fundamental gneisses and the intrusives is in general recognisable in many cases. The three elements of the great basement complex of the Himalayas are thus mixed up and may best be described a t this place : (1) the metamorphosed sedimentary Archaeans, (2) intrusive 1 Pilgrim and West, Mem. G.S.I. vol. liii, 1928; J. B. Auden, Rec. G.S.I. vol. lxvii. pt. 4, 1934.

G E O L O G Y O F K A S H M IR

397

granite and gneisses of later periods, (3) remnants of Archaean granites, granulites, ortho-gneisses and schists. The presence of the latter can be inferred from the occurrence of granite pebbles and boulders, beds of arkose and of the widespread quartzites in the Palaeozoic sediments. The gneisses have often assumed a coarse granitoid aspect, while owing to extreme dynamic metamorphism, the very much younger intrusive granites have developed a gneissic struc­ ture. Foliation thus is not a criterion of age. Petrology—Three kinds of granite have been recognised in this complex: biotite-granite, hornblende-granite and tourmalinegranite. Of these the most prevalent is the biotite-gneiss or granite, the one showing a quick transition to the other. The composition is acidic ; pink orthoclase is rare, so also-is muscovite ; the bulk of the gneiss is made up of milk-white orthoclase, acid plagioclases with quartz and a conspicuous amount of biotite, arranged in schistose or lenticular manner, foliation being fine, or coarse, or absent altogether. This rock is the most prevalent Himalayan gneiss from Kashmir to Assam, I t is often porphyritic, with orthoclase phenocrysts as much as 2-4 inches across, giving rise to an apparent augen structure. Accessory minerals are not common except garnet and tourmaline. Hornblende-gneiss is much less common, but it has a very similar structure and composition, the biotite being replaced by hornblende, sometimes not completely. Sphene is a common accessory. Both the gneisses are traversed by veins of intrusive tourmaline-granite varying from a foot to 20 or more feet in breadth, which in some cases pene­ trate the surrounding sedimentary strata as well. These pegmatite and aplite veins have a greater diversity of mineral composition than their hosts, often carrying such accessories as microcline, oligoclase, rock-crystal, garnet, tourmaline (schorl as well as the coloured trans­ parent varieties rubellite and indicolite), muscovite, beryl (aqua­ marine), fluorspar, actinolite, corundum. Next to the gneisses the most frequent rock is biotite-schist, passing into fine, thinly foliated, silky schists, such as chlorite-, talc-, horn­ blende-, muscovite-, schists. These rocks are abundantly traversed by dykes, stocks and masses of basic intrusives such as dolerite, epidiorite, gabbro, pyroxenite, etc. Distribution—With regard to the distribution of the gneissic rocks in the area, the main crystalline development is in the north and north­ east portions, in the Zanskar range and the region beyond it, in Gilgit, Baltistan and Ladakh, while in the ranges to the south of the valley they play but a subordinate part. The core of the Dhauladhar range

398

GEOLOGY OF IN D IA

is formed of these rocks, but they are not a very conspicuous com­ ponent of the Pir Panjal range, where they occur in a number of minor intrusions. The trans-Jhelum continuation of this range, known as the Kaz Nag, has a larger development of the crystalline core. A broad area of Kishtwar is also occupied by these rocks which continue in force eastwards to beyond the valley of the Sutlej. I t is from the circumstances of the prominent development of the crystalline core in the Zanskar range, in continuity with the central Himalayan axis, th at the range is regarded as the principal continuation of the Great Himalayan chain, after its bifurcation a t Kangra. The other branch, the Pir Panjal, is regarded only as a minor offshoot. North of the Zanskar the outcrop of the crystalline series becomes very wide, en­ compassing almost the whole of the region up to the Karakoram, with the exception of a few sedimentary tracts in central and south-east Ladakh. The largest occurrence of hornblende-granite is in the moun­ tains between Astor and Deosai. Its post-Cretaceous age is definitely proved by its intrusive contact with Orbitolina limestone a t the head of the Burzil valley. Tourmaline-granite is of relatively subordinate occurrence in pegmatite veins. THE SEDIMENTARY PRE-CAMBRIAN SYSTEMS—THE SALKHALA SERIES The name Salkhala series is given to the oldest sedimentary rocks of the Kashmir Himalaya consisting of slates, phyllites and schists, with interbedded crystalline limestones and flaggy quartzites. I t forms the basement of the unfossiliferous Purana slates and the subsequent sedimentary systems of Kashmir. Its relations with the newer rocks are generally a profound unconformity or thrust-fault. Graphitic slate and crystalline limestones (dolomitic), occasionally inarble-beds, black or snow white, are prominent elements of the Salkhalas. Dynamic metamorphism, generally of a high grade is evident in the series, but all types of rocks are met with from dense compact carbonaceous slates and finely crystalline limestones to adinole-like beds, micaceous, garnetiferous and graphitic schists, saccharoidal marble, calc-schist and gneisses. The Salkhala sediments have been subjected to an in­ tense granitisation a t places, in Kaghan, in the ranges north of the Kishenganga, and in the Nanga Parbat area. The argillaceous com­ ponents have been converted by the injection of magma to biotitegneisses ; white the calcareous and dolomitic members are changed into dark hornblende and garnet gneisses. A host of secondary

G E O L O G Y O F K A S H M IR

399

minerals have resulted from metamorphic action—phlogopite, actinolite, epidote, zoisite, sphene, idocrase, tourmaline, beryl, etc. Else­ where the metamorphism is of a curiously subdued type and the Sal­ khala slates, then, are scarcely distinguished from some Dogra slates. Stratigraphically as well as lithologically the Salkhalas are akin to the Jutogh series of the Simla area, and it is probable that a continu­ ous outcrop of these rocks stretches from Simla to Kaghan through the Dhauladhar range. The prominent peak of Nanga Parbat, Mt. Diyamir, 26,620 feet, the culminating point of the Punjab Himalaya, is composed almost en­ tirely of finely schistose biotite-gneiss, a para-gneiss, with interbedded marble, graphite-schists, etc., of Salkhala age. Through this paragneissic complex are intruded sheets and bosses of gneissose granite of two later periods.1 PALAEOZOIC GROUP Dogra slates—Underlying the fossiliferous Cambrian of Kashmir conformably, and at some localities showing a transitional passage into them, there is a thick zone of slaty rocks—argillaceous cleavage slates, with generally oblique cleavage, with thin sandy or quartzitic partings, often ripple-marked. They are quite unfossiliferous and their exact horizon, whether Purana or possibly Lower Cambrian, is uncertain. A lithologically identical group occurs in Hazara and Simla, recognised as Hazara slates and Simla slates. The Dogra slates occupy long belts in the Pir Panjal (wThere they are associated with a great thickness of contemporaneous basic trap), the Kishenganga valley and in Hazara. Basins of Palaeozoic rocks—Fossiliferous Palaeozoic rocks of Kash­ mir occupy elongated ellipse-shaped patches of the country north of the alluvial part of the valley, stretching from north-west of Hundawar to the south-east end of the Kashmir sedimentary “ basin*”, where it merges into the Spiti basin. The Lidar valley development is the more typical. The long axis of this ellipse, north-west to south­ east, corresponds to the axis of a broad anticlinal flexure, in which the whole series of Palaeozoic rocks is folded. Denudation has exposed, in the central part of this anticlinal, a broad oval outcrop of the most ancient fossiliferous rocks of Kashmir—the Cambrian and Ordovician —flanked on its two sides successively by thinner bands of the younger formations, Silurian, Devonian and Carboniferous (see PI. VIII). A 1 Wadia, Geology of Nanga Parbat and parts of Gilgit District, Rec. O.S.I., vol. lxvi. pt. 2, 1932.

G EO L O G Y O F IN D IA

G E O L O G Y O F K A S H M IR

US

* e, a^ 7gS 3 73

C« *3 cS 93 as ^i &g Sausar series, 76. Sahyadri mountains, 12, 32. / Schuchert, Prof. Charles, 134. Salajit, 254 (note). Schwagerina limestone, 164. Salem gneiss, 63. Scolecite, 217. Salisbury, R. D., 167. Sehta, 355. Salkhala series, 81, 82, 398. Semri series, 95. Salses (mud volcanoes), 27, 28. Serpentine, 70, 196, 201, 336, 358. Salt, Kohat, 246, 362, 363. Shamsh Abari syncline, 401, 404. ■ lakes, 22, 324. Shan States,'N., map of, Plate XX. marl, 245. Cambrian of, 351. potash, 245. geological formation of, 117-121. sources of, 362. Jurassic of, 183. wells, 362. Palaeozoic section of, 117, 164. wind-borne, 23, 362. Silurian of, 117, 403. Salt-beds, 245, 290, 363. Triassip of, 175. Saltpetre, 364. Shillong series, 76. Salt-pseudomorph shales, 104, 107, 153. quartzites, 200. Salt-Range, Index map to, Plate XVIII. Shyok glacier dam, 39. Salt-Range a dislocation mountain, 317. Siachen glacier, 13. Cambrian of, 104-108, 153. Carboniferous and Permian of, 153- Sikkim, 7, 321, 389. _ 159. copper-ores of, 345. hanging valleys of, 20, 278. coal of, 338, 339, 377. Sillimanite, 58, 59, 63, 65, 369. Crctaccous of, 200.

Rann of Cutch, 5, 23, 33, 292, 307. Rare minerals, 376-377. Ratanpur, agates of, 360. Ravi river, 260, 384. Realgar, 354. Recent deposits, 299-307, 437, 438. Recession of the watershed, 19. Regur, 37, 221, 299, 305, 380. Reh, 37, 289, 366, 381. Rejuvenation of the Himalayan rivers, 34, 283, 322. “ Relict ” mountains, 2, 309. Remo glacier, 13. Rewah series, 95, 97, 356. Rhyolites, Malani, 96. Pawagarh, 214. Riasi, coal-measure of, 339, 432. Permo-Carboniferous inlier of, 418419. Rift-valley, 4, 283. Rifts, 320. Ripple-marks, 94, 107. River action in India, 17, 19, 20, 39. capture, 20. erosion, 37, 38. Roches moutonne.es, 155, 390. Rock-basins, 21, 324, 388. -crystal, 85, 217, 361. -meal, 390. -salt 245, 246, 363. Rohtas limestone, 96. Rubelhte, 360, 397. Rubies, 85, 117, 356, 368. Rupshu, Cretaceous rocks of, 426. Rutile, 376.

458

GEOLOGY OF IN D IA

Silurian system, of Burma, 117-121. of Kashmir, 115, 403-404. of Shan States, 117-121, 403. of Spiti, 111-112. Silver, 351. Simla Himalayas, Tertiaries of, 234. slates, 82, 100, 399. Sind, 34, 48, 198, 231, 240, 252. Cretaceous of, 198-199. Oligocene of, 252-253. Ranikot system of, 232, 240. river, 20. Siwaliks of, 263, 274. Tertiary of, 230, 231-232, 242, 252, 274. Singar mica-mines, 375. Singareni coal-field, 134, 135, 338. Singhbhum, asbestos of, 373. copper-ores of, 345. manganese of, 80. Singu oii-field, 342. Sir ban limestone, 163. Mount, geology of, 172. Sirmur system, 264, 316. Sitaparite, 80. Sivamalai series, 59. Sivapithecus, 273. Sivasamudram falls, 17 (note). Siwalik river, 40, 269. Siwalik system, 263-275, 337, 435-437. composition of, 269-270. fauna of, 266-269, 271-273, 281, 435. homotaxis of, 274. Boundary Fault of, 264-265. of Burma, 263, 274. of Kashmir, 301, 435-437. of Salt-Range, 271. of Sind, 263, 274. structure of, 263-266. Siwana granite, 96. Slate, 70, 91, 337. quarries of, 337. Smithsonite, 355. Snow-line of the Himalayas, 13. Soan river, 41. Sodium chloride, 23, 245. 246, 290, 324, 362. Sohagpur coal-field, 338. Soil-creep, 42. Soils of India, 378-381. Solfataras, 90. Songir sandstone, 207, 336. Spandite, garnet, 80. Speckled sandstone series, 134, 155. Spinel, 85, 117, 357. Spiti, basin? 47, 108. Cambrian of, 108. Carboniferous of, 159-161. Cretaceous of, 193-195. Devonian of, 112, 115. geological province, 108. geosyncline, 108.

Spiti gypsum of, 372. Jurassic of, 178-180, 424. Palaeozoic of, 108, 111-115. shales, 169, 179, 180, 424. Silurian of, 111, 112. Triassic of, 166, 168-172 Springs, 328, 329, 422. mineral, 90, 329. radio-active, 330. Sripermatur beds, 146. Stalagmite, 299, 304. Steatite, 371. Stibnite, 354. Stilbite, 217. Stoliczka, F., 396, 427. Stone Age in India, 300, 306. implements, 297, 300, 306. Stratigraphy of India, 2, 43-54. Subathu series, 235, 248, 431. Sub-Him&layan zone, 10, 383. Submerged forests, 33. Suess, Eduard, 4, 282. Suket shales, 94, 95. Sulcacutus beds, 178, 180. Sullavai sandstones, 96. Sulphur, 339, 377-378. Sulphuric acid, 343, 365, 378. Surat, Tertiary deposits of, 227. Surma series, 260. Sutlej, ossiferous alluvium of, 299. Sven Iledin, 195, 389. Syenite, augite-, 261. nepheline-, 59, 214, 377. Sylvite, 363. Synclinorium, 283. of Aravalli range, 74. of Indo-Gangetic plains, 283, 284. Syntaxis of N. W., Himalaya, 8. Syringothyris limestone, 405. Systems of Southern India, Index map to, Plate X XI. T Tachylite, 213. Tagling stage, 179, 180, 425. Tal series, 181. Talchir boulder-bed, 129, 131, 134, 412. flora, 127, 131, 132, 134. fossils, 131. series, 126, 129, 130, 131, 134. Tanawal series, 409. Tandur coalfield, 338. Tanr, 301. Tantalite, 377. Tapti river, 17, 18, 299, 300. old alluvial remains from, 300. Tavoy, tin of, 352. wolfram of, 353. Tectonic lakes, 21, 324. mountains, 3, 309, 310.

IN D E X Tectonic valleys, 320. Terai, 289. Teri, 299, 302. Terra-cotta, 135, 330. Tertiary systems, 223-239, 428-430. distribution and facies of, 225-227. earth-movements in, 223, 261. fauna of, 223, 228, 230, 231, 262, 429. of Burma, 237-239, 341. of Coromandel coast, 230. of Cutch, 225, 226, 227. of Extra-Peninsula, 225, 231-239. of Gujarat, 227. of Himalayas, 223, 224, 234-236, 310. of Kashmir, 235, 428-430. of Kathiawar, 228. of Rajputana, 230. of Salt-Range, 232-234. of Sind, 231-232. of Travancore, 230, 231. rise of Himalayas in, 224, 225, 308309. Tethys, the, 121, 124, 149, 181, 182, 196, 208, 224, 410, 428, Thar, the, 190, 290. Thomsonite, 217. Thorianite, 377. Thrust-plane, 6, 264, 310, 440. Tibetan lakes, 21, 22. zone of the Himalayas, 9, 196, 312. Tiki stage, 130. Tiles, 331. Tin, 352. Tinnevelli submerged forest, 33. coast, 302. Tipam series, 274. Tipper, G. H., 116, 195. Tista river, 20. Titanium, 294, 376. Tonkinella, 401. Tourmalines, 57, 85, 196, 353, 360. Trachyte, 214. Transition systems, 101. Traps, as building stone, 337. Bijawar, 90. Deccan, 91, 190, 193, 211-222, 337, 347, 360, 380. Panjal, 405, 409-414. Rajmahal, 143, 295. Travancore, 24, 231. Eocene of, 225. graphite of, 371. monazite of, 370, 377. Tertiary beds of, 230, 231. Travertine, 332, 439. Triassic system, 166-176, 420-424. fauna of, 166, 170-172, 175, 177, 423. of Baluchistan, 166, 174. of Burma, 166, 175. of Hazara, 172. of Himalayas, 168-169.

459

Triassic system, of Kashmir, 175, 420424. of Salt-Range, 166, 173-174. of Spiti, 166, 168-169. Trichinopoly marble, 203, 334. stage, 203, 374. Tripetty sandstone, 145. Tropites beds, 169. Tsomoriri lake, 21, 324, 388, 391. Tungsten, 84, 353. U Umaria coal-field, 135, 338. Marine Permo-Carboniferous, 164. Umia series, 147-148, 189-190, 199, 336. Unconformity, Purana, 101-102. Upper Carboniferous, 114, 149, 408. Upper Palaeozoic, 149. Underclay, 331. Upper Carboniferous system. See under Carboniferous. Upper Murree, 259,434. Uranium, 375. U tatur stage, 203. V Vaikrita series, 81, 108. Valleys, drowned, 25. erosion, 320, 321. hanging, 20, 279. tectonic, 320. transverse, of the Himalayas, 19, 321, 387. Vallum diamonds, 361. Vanadium, 376. Varved clays, 301, 438. Vemavaram beds, 146. Verde antique, 336. Vihi district, 414, 416. Vihi district, Plan of, Plate XIV. Vindhya hills, 11, 93, 95, 318. Vindhyan system, 93-102. composition of, 93-94. diamonds in, 96, 99, 356. earth-movements in, 94, 97. homotaxis of, 101. limestones of, 94, 95, 96, 99, 351. Lower, 95-97. of Extra-Peninsula, 99-100. sandstones of, 94, 95, 96, 97, 98, 300, 336, 356, 369. Upper, 97-99. Virgal beds, 154. Vizagapatam, Kodurite series of, 77, 360. stibnite of, 354. Volcanio basins, 324. islands, 25, 26. phenomena, 23, 25-27, 193, 195-197, 208, 209, 211-221, 410, 411-414.

GEOLOGY OF IN D IA

Volcanoes, 25-28. mud, 27. Vredenburg, E. W., 101, 137, 182 (note), 238. Vredenburgite, 80. W Wad, 80. Wadia, D. N., 8, 384, 392, 412. Warkalli beds, 230. Water, as an economic product, 327-330. Waterfalls, 17, 77, 323. Watershed of the Himalayas, 19. of the Peninsula, 17. recession of, 20. Weathering, 11, 63, 68, 221, 308, 434. Wells, 292, 328. artesian, 328. inverted, 329. tube, 329. West, W. D., 85, 396, 442. Western Ghats, 11, 12, 32. Wetwin slates, 119, 120. Winchite, 80. Wind-blown sand, 4, 23, 229, 290-292, 302. “ Windows ” in nappes, 311, 442.

Wolfram, 353, 377. Woodward, Sir Arthur Smith, 209, 220. Wootzi, 347. Wular lake, 21, 388. Wynne, A. B., 293 (note). Y Yamdok Cho, 21. Yellaconda hills, 87. Yenangyat oil-field, 342. Yenangyaung oil-field, 28, 341, 342. Yenna falls, 17 (note). Z Zamia shales, 189. Zanskar range, 224, 236, 357, 368, 383, 385, 389, 397. river copper, 346. sapphires in, 357, Zebingyi series, 118, 121. Zemu glacier, 14. Zeolites, 217. Zewan series, 162, 416-418. Zhob, chromite, at, 354. Zinc, 352. Zircon, 85, 359, 375, 377,

T'R IN TE D IN G REA T B R IT A IN B Y R O B E R T M ACLEHOSE AND CO. L T D . T H E U N IV E R S IT Y P R E S S , GLASGOW

Survey of India, Records, vol. xl. pt. 3.)

460

PLATE XIV. PLAN OF

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